阅读说明：本技术 Rna分子与肽的复合体的制造方法及其利用 (Method for producing complex of RNA molecule and peptide, and use thereof ) 是由 上田泰己 清水义宏 原田颂子 松本桂彦 于 2018-03-15 设计创作，主要内容包括：本发明提供一种高效地获得复合体的方法及其利用,所述复合体是将基因(mRNA)与作为其翻译产物的肽经由肽受体分子而连结。本发明的方法中,在模板DNA的反义链的5’末端侧导入至少一个2’-修饰核苷衍生物。(The present invention provides a method for efficiently obtaining a complex in which a gene (mRNA) and a peptide that is a translation product thereof are linked via a peptide receptor molecule, and use thereof. In the method of the present invention, at least one 2 '-modified nucleoside derivative is introduced into the 5' -terminal side of the antisense strand of the template DNA.)

1. A method for producing a complex of an RNA molecule and a peptide, which comprises producing a complex of an RNA molecule encoding a peptide and a peptide encoded in the RNA molecule, the method comprising:

step (i): a step of preparing an RNA molecule by transcription reaction of a DNA molecule comprising a promoter region and a region encoding a peptide located downstream thereof, wherein the DNA molecule comprises at least one 2 '-modified nucleoside derivative on the 5' -terminal side of the most downstream antisense strand;

step (ii): (ii) a step of binding a peptide receptor molecule at the 3' end of the RNA molecule obtained in step (i) using a splint polynucleotide as a scaffold; and

step (iii): (iii) a step of producing a complex of the RNA molecule, the RNA molecule linked to a peptide encoded in the RNA molecule via the peptide receptor molecule, and the peptide by translating the RNA molecule to which the peptide receptor molecule is linked, the RNA molecule being obtained in step (ii).

2. The method of claim 1,

the translation is performed in an in vitro translation system that does not substantially contain ribonucleases.

3. The method according to claim 1 or 2,

the translation is performed in an in vitro translation system that does not substantially comprise an RNA polymerase active on the DNA molecule.

4. The method according to any one of claims 1 to 3,

the DNA molecule comprises two 2' -modified nucleoside derivatives in series.

5. The method according to any one of claims 1 to 4,

the 2 '-modified nucleoside derivative is 2' -O-methylguanosine.

6. The method according to any one of claims 1 to 5,

the peptide receptor molecule is puromycin.

7. The method according to any one of claims 1 to 6,

using a plurality of different said DNA molecules to make said complexes of a plurality of different RNA molecules and peptides.

8. An mRNA display method comprising the method according to any one of claims 1 to 7,

comprising a step (iv) of selecting a desired complex from the complexes of the RNA molecule and the peptide obtained in the step (iii).

9. The method of claim 8,

the steps (i) to (iv) are repeated for a plurality of cycles as one cycle.

10. A DNA library for use in mRNA display method,

comprising a plurality of different candidate DNA molecules comprising a promoter region and a region encoding a candidate peptide located downstream thereof, and comprising at least one 2 '-modified nucleoside derivative on the 5' -terminal side of the most downstream antisense strand.

11. The DNA library according to claim 10,

comprises 10¹³More than one different candidate DNA molecule.

Technical Field

The present invention relates to a method for producing a complex of a ribonucleic acid (RNA) molecule and a peptide encoded in the RNA molecule, and use thereof.

Background

In recent years, development of molecular targeted drugs represented by antibody drugs has been actively carried out, and the market size thereof has been expanding. However, for further development, a method for efficiently screening "high-quality antibodies" having higher specificity or affinity for antigens has been desired. In addition, although there are many stubborn diseases or chronic diseases of unknown cause at present, the problem of "exhaustion of drug development target" is pointed out because the cause investigation has not progressed.

Analysis of proteins is generally more difficult than genetic analysis. As for genes, various gene amplification methods such as a Polymerase Chain Reaction (PCR) method have been developed, and it is easy to prepare a large amount of samples, and one of the reasons for this is that there is no direct amplification method for proteins.

Therefore, as an example of a method for facilitating the analysis of a protein, a method has been developed which utilizes a complex in which a protein directly binds to a gene encoding the protein.

For example, patent document 1 and non-patent documents 1 to 2 disclose the following methods: functional peptides are selected using a complex in which a gene (messenger ribonucleic acid (mRNA)) and a peptide that is a translation product thereof are covalently bonded via puromycin (puromycin). More specifically, the gene (mRNA) and a peptide that is a translation product thereof are linked via puromycin by linking puromycin to the 3' -end of the gene (mRNA) via a predetermined linker and translating the gene. These methods are also called mRNA display method, in vitro virus (Invitro virus) method, etc., and can use a method including 10¹³～10¹⁴A method for the preparation of very large libraries of about said complexes. In addition, as a method derived from the above method, a method has been developed in which mRNA is converted into complementary deoxyribonucleic acid (cDNA) and then usedcDNA display method, RAPID display method using unnatural amino acids, or the like.

In the mRNA display method, several methods have been developed as a method for linking a gene (mRNA) to puromycin or a puromycin substitute (collectively referred to as a peptide receptor molecule or a peptide receptor). When the mRNA display method was first developed, a method using DNA called splint DNA as a scaffold was the mainstream. More specifically, the method hybridizes the linker comprising the peptide receptor molecule to the 3 '-end side of the gene (mRNA) with respect to the same splint DNA, and enzymatically links the linker to the 3' -end side of the gene (mRNA) (non-patent document 3, etc.).

However, a method of using a linker having a side chain base at one end that is paired with a base sequence on the 3' -end side of mRNA and a peptide receptor molecule at the other end has been mainstream as a method of linking a gene (mRNA) and a peptide receptor molecule (see also patent document 2 and the like). In the case of using the linker as described above, the one end of the linker is hybridized with the base sequence on the 3 '-end side of the mRNA, and then, the one end of the linker is enzymatically linked with the 3' -end of the mRNA to form a hairpin (hairpin) structure.

[ Prior art documents ]

[ patent document ]

[ patent document 1] WO98/31700 (International publication on 23/7/1998)

[ patent document 2] WO2011/049157(2011, International publication on 28 th month 4)

[ non-patent document ]

[ non-patent document 1] RNA-peptide fusions (RNA-peptide fusions) for the in vitro selection of peptides and proteins. Journal of the National Academy of Sciences of the United States of America, Proc. Natl. Acad. Sci. USA), 94: 12297-.

[ non-patent document 2] in vitro virus: binding of mRNs with puromycin at the 3 '-end on In vitro ribosomes to the C-terminus of the protein encoded thereby (In vitro viruses: binding of mRNA bearing puromycin to the 3' -terminal end of the C-terminal end of encoded protein In vitro). Federal on the European Biochemical society Letters, FEBS Letters, 414: 405-.

[ non-patent document 3] Optimized Synthesis of RNA-Protein Fusions for in Vitro Protein Selection (Optimized Synthesis of RNA-Protein Fusions for in Vitro Protein Selection). METHODS IN ENZYMOLOGY (METHODS IN Enzymogy), VOL.318, P268-293,2000.

Disclosure of Invention

[ problems to be solved by the invention ]

The method using a splint DNA described in non-patent document 3 and the like has a problem that the ligation efficiency of both the base sequence at the 3' -end of the gene (mRNA) and the base sequence of the linker containing puromycin is significantly reduced unless both the base sequences are strictly controlled.

On the other hand, the method of linking a gene (mRNA) to a peptide receptor molecule (formation of a hairpin structure) described in patent document 2 and the like is more preferable than the method using a splint DNA in the following respects: 1) does not require splint DNA, 2) there is a certain margin in the stringency of hybridization between the base sequence at the one end of the linker and the base sequence on the 3' -end side of mRNA (enzymatic ligation is possible even with a variation of one to several bases).

However, since the mRNA display method is a method including various steps in addition to the step of linking the gene (mRNA) and the peptide receptor molecule, it is considered that there is still a large room for improvement from the viewpoint of efficiently obtaining a complex in which the gene (mRNA) and the peptide as a translation product thereof are linked.

An object of one embodiment of the present invention is to provide a method for efficiently obtaining a complex in which a gene (mRNA) and a peptide that is a translation product thereof are linked via a peptide receptor molecule, and use thereof.

[ means for solving problems ]

The present inventors have conducted active studies on the above-mentioned problems. As a result, it has been found that a method of connecting a gene (mRNA) to a peptide receptor molecule using a splint DNA is surprisingly excellent in terms of efficiently obtaining a complex of the gene (mRNA) and a peptide as a translation product thereof. Based on the above findings, the present invention was conceived as a result of focusing attention again on a method using splint DNA.

In order to solve the above problem, one aspect of the present invention is as follows.

(1) A method for producing a complex of an RNA molecule and a peptide, which comprises:

step (i): a step of preparing an RNA molecule by transcription reaction of a DNA molecule comprising a promoter region and a region encoding a peptide located downstream thereof, wherein the DNA molecule comprises at least one 2 '-modified nucleoside derivative on the 5' -terminal side of the most downstream antisense strand;

step (ii): (ii) a step of binding a peptide receptor molecule at the 3' end of the RNA molecule obtained in step (i) using a splint polynucleotide as a scaffold; and

step (iii): (iii) a step of producing a complex of the RNA molecule, the RNA molecule linked to a peptide encoded in the RNA molecule via the peptide receptor molecule, and the peptide by translating the RNA molecule to which the peptide receptor molecule is linked, the RNA molecule being obtained in step (ii).

(2) A DNA library for mRNA display comprising a plurality of different candidate DNA molecules comprising a promoter region and a region encoding a candidate peptide located downstream thereof, and comprising at least one 2 '-modified nucleoside derivative on the 5' -terminal side of the most downstream antisense strand.

[ Effect of the invention ]

According to one aspect of the present invention, it is possible to provide a method for efficiently obtaining a complex in which a gene (mRNA) and a peptide that is a translation product thereof are linked via a peptide receptor molecule, and use thereof.

Drawings

Fig. 1 is a diagram illustrating a difference between an example of a conventional method and an example of the method of the present invention.

FIG. 2 is a graph showing the results in example 1.

FIG. 3 is a graph showing the results in example 2.

FIG. 4 is a graph showing the results in example 3.

FIG. 5 is a diagram for explaining a method of eluting cDNA using protease in example 4.

FIG. 6 is a graph showing the results in example 4.

Fig. 7 is a diagram illustrating another example of the method of the present invention.

FIG. 8 is a graph showing the results in example 5.

Detailed Description

The method for producing a complex of an RNA molecule encoding a peptide and a peptide encoded in the RNA molecule according to the present invention comprises:

step (i): a step of preparing an RNA molecule by transcription reaction of a DNA molecule comprising a promoter region and a region encoding a peptide located downstream thereof, wherein the DNA molecule comprises at least one 2 '-modified nucleoside derivative on the 5' -terminal side of the most downstream antisense strand;

step (ii): (ii) a step of binding a peptide receptor molecule at the 3' end of the RNA molecule obtained in step (i) using a splint polynucleotide as a scaffold; and

step (iii): (iii) a step of producing a complex of an RNA molecule and a peptide, in which the RNA molecule and the peptide encoded in the RNA molecule are linked via the peptide receptor molecule, by translating the RNA molecule to which the peptide receptor molecule is bound, which is obtained in step (ii).

Hereinafter, embodiments of the present invention will be described in detail.

(definition)

The term "library" as used herein refers to a collection of a plurality of (two or more) different molecules (e.g., a plurality of different DNA molecules, a plurality of different RNA molecules, or a plurality of different RNA-peptide complexes), and refers to, for example, a collection of molecules classified into the same classA collection of multiple different molecules of a domain (e.g., a domain of a DNA molecule, a domain of an RNA molecule, or a domain of an RNA-peptide complex). The names of the molecular domains are sometimes referred to as a DNA library (a library of DNA molecules), an RNA library (a library of RNA molecules), an RNA-peptide complex library (a library of RNA-peptide complex molecules), and the like. In the method according to the present embodiment, since selection from a plurality of candidate molecules is easy as necessary, the "library" in the present embodiment may preferably contain 10⁹More than one, more preferably 10¹⁰More than 10¹¹More than or equal to, or 10¹²More than one, more preferably 10¹³More than one different molecule.

By "selecting" is meant substantially distinguishing a molecule from other molecules in a population, e.g., substantially distinguishing a molecule from a collection of multiple different molecules classified in the same category. As used herein, by "sorting/selecting", a desired molecule can be concentrated to at least 2 times, preferably 30 times or more, more preferably 100 times or more, and further preferably 1000 times or more after sorting, compared with molecules in a library which are not the desired molecule. As described in the present specification, the sorting stage may be repeated any number of times in a predetermined method, and different types of sorting stages may be combined.

(existing method)

Before describing the method according to the present embodiment, an example of a conventional mRNA display method using a splint polynucleotide (DNA) will be briefly described with reference to fig. 1 (a).

In one example of the conventional mRNA display method, the following steps are performed.

(1) First, a library of candidate DNA molecules encoding candidate peptides is prepared. The candidate DNA molecule is usually double-stranded, and has a structure in which a region encoding a peptide is arranged downstream of a promoter region recognized by RNA polymerase used in the transcription reaction in step (2). On the upstream side of the region encoding the peptide, there is a translation initiation sequence (e.g., initiation codon) suitable for the cell-free translation system used.

(2) Then, a transcription reaction is performed by allowing an RNA polymerase to act on the candidate DNA molecules, thereby preparing a library of corresponding candidate RNA molecules. Then, the prepared candidate RNA molecules are separated from other transcription reaction components.

(3) Subsequently, a linker having a peptide receptor molecule (e.g., puromycin) bound to the 3 'terminus is ligated to the 3' terminus of the candidate RNA molecule. The linker comprises nucleotides, and a peptide receptor molecule is bound to the 3' end of the nucleotides. Polyethylene glycol (PEG) may also be inserted between the nucleotide and the peptide receptor molecule. For binding of a candidate RNA molecule to the linker, an oligonucleotide (e.g., "splint DNA") referred to as a "splint polynucleotide" may also be used. In this case, a splint polynucleotide comprising a sequence that can hybridize on the 3'-terminal side of the candidate RNA molecule and a sequence that can hybridize on the 5' -terminal side of the nucleotide of the adaptor is used as a scaffold. That is, the splint polynucleotide includes a sequence complementary to the sequence on the 5 '-end side of the adaptor and a sequence complementary to the sequence on the 3' -end side of the candidate RNA molecule adjacent thereto. Candidate RNA molecules ligated via the splint polynucleotide are ligated (bound) to the ligate by, for example, a reaction using T4DNA ligase. In addition, one to several bases are added to the 3' -end of the candidate RNA molecule at an arbitrary frequency (for example, about 50%) depending on the characteristics of the RNA polymerase used in step (2). Therefore, the library prepared has candidate RNA molecules to which one to several bases are added at the 3' end. The ligation efficiency may decrease due to the heterogeneity of the 3' terminal sequence. Subsequently, purification is performed to remove unligated candidate RNA molecules. Here, when the unlinked candidate RNA molecule is removed, a peptide that does not form a complex with RNA in step (4) is generated, and when it comes into contact with the binding partner in step (6), the efficiency of obtaining the target candidate RNA-peptide complex decreases.

(4) Then, the candidate RNA molecule is translated in a cell-free translation system to produce a candidate RNA-peptide complex in which the candidate RNA molecule and the corresponding candidate peptide are linked via the linker. Subsequently, purification is performed by removing the intermediate in the cell-free translation system (high concentration of Mg or K, etc.) in order to allow the reverse transcription reaction of step (5) to proceed.

(5) Then, a reverse transcription reaction is performed to make the candidate RNA molecule portion of the candidate RNA-peptide complex double-stranded with a dna (cdna) molecule for the purpose of preventing degradation by ribonuclease (RNase). Thereby creating a library of candidate RNA-peptide complexes.

(6) Then, the library of candidate RNA-peptide complexes is contacted with a binding partner (e.g., an antibody immobilized on a solid support) to perform a binding reaction. Candidate RNA-peptide complexes that are not bound to the binding partner are removed by washing with, for example, a buffer or the like.

(7) Subsequently, the candidate RNA-peptide complex is dissociated from the binding partner, and the candidate RNA-peptide complex is recovered. As described above, the desired RNA-peptide complex is selected from a library of candidate RNA-peptide complexes.

(8) Subsequently, cDNA was amplified by PCR. Using the amplification product, returning to step (2), repeating the same operation, and concentrating the target candidate RNA-peptide complex.

(method of the present embodiment)

An mRNA display method using the method according to the present embodiment will be described in detail with reference to fig. 1 (B).

[ step 1]

In step 1, a library of candidate DNA molecules is prepared, comprising a plurality of different candidate DNA molecules comprising a promoter region and a region encoding a candidate peptide located downstream thereof, and comprising at least one 2 '-modified nucleoside derivative on the 5' -terminal side of the most downstream antisense strand.

The term "peptide" as used herein refers to a compound in which two or more amino acids are bonded by peptide bonds. The number of amino acids is not limited, and may be, for example, 2 to 1000, preferably 4 to 200, more preferably 6 to 100, and still more preferably 7 to 10. The peptide may be, for example, a fragment or full length of the protein. In one example, the peptide may be an antibody (e.g., scFv) or a fragment thereof.

The candidate DNA molecules may be either molecules with known or unknown sequence. The sequence may be a sequence based on a sequence existing in nature as genomic information (for example, a cDNA obtained by reverse transcription of an mRNA existing in nature), or a sequence designed artificially. For example, the sequence may be one synthesized randomly by organic synthesis, or may be one obtained by encoding a protein whose sequence is unknown by insertion of random variation by a PCR method.

The candidate DNA molecule comprises a region encoding a candidate peptide. The candidate DNA molecule optionally contains a region (transcription control region) for transcription using the antisense strand as a template. Examples of the transcription control region include a promoter region. These transcription control regions may be appropriately selected depending on the type of RNA polymerase used in the transcription reaction in step 2. In one example, the promoter region may be a promoter recognized by T7RNA polymerase, SP6 RNA polymerase, or T3 RNA polymerase (T7 promoter, SP6 promoter, or T3 promoter).

The candidate DNA molecule including the promoter region and the region encoding the candidate peptide located downstream thereof may be single-stranded or double-stranded as long as the candidate RNA molecule encoding the peptide is produced by transcription reaction, and they may be present in a mixture (a part of them is double-stranded, and they are also single-stranded).

In detail, the promoter region in the candidate DNA molecule may be single-stranded or double-stranded as long as the candidate RNA molecule encoding the candidate peptide is transcribed from the region encoding the candidate peptide located downstream, and for example, a part of the promoter region may be composed of a single strand (sense strand or antisense strand), and the other part may be double-stranded. As described above, a promoter region partially composed of a single strand (sense strand or antisense strand) is also included in the "promoter region" in the present specification. Transcribing the candidate RNA molecule encoding the candidate peptide if the promoter region does not exhibit promoter activity. Promoter activity can be determined using methods well known in the art. Alternatively, transcription of a candidate RNA molecule encoding a candidate peptide can be confirmed by detecting an RNA molecule by a method known in the art, detecting a peptide produced by translation, or the like.

Furthermore, the region encoding the candidate peptide in the candidate DNA molecule may be single-stranded or double-stranded as long as the candidate RNA molecule encoding the candidate peptide is transcribed by the action of the upstream promoter region, and these may be present in a mixture, for example, the entire encoding region may be single-stranded (sense strand or antisense strand). Since the candidate RNA molecule is transcribed using the sequence of the antisense strand as a template, the region encoding the candidate peptide preferably contains at least the antisense strand. The region partially or entirely composed of a single strand (sense strand or antisense strand) as described above is also included in the "region encoding a peptide" in the present specification. The region encoding the candidate peptide comprises at least the antisense strand, and preferably comprises at least one 2 '-modified nucleoside derivative at the 5' -terminal side of the antisense strand most downstream of the candidate DNA molecule.

The candidate DNA molecule optionally comprises a sequence for translation of the candidate RNA molecule. The sequence for translating the candidate RNA molecule may be appropriately selected according to the type of ribosome used in step 4. When a ribosome derived from Escherichia coli is used as a cell-free translation system, the efficiency of the translation reaction is increased by including a Shine-Dalgarno (SD) sequence as a ribosome binding sequence upstream of the initiation codon. In the case of using a cell-free translation system derived from eukaryotes, a Kozak sequence that facilitates initiation of translation may also be present. In addition, a 7-methylated guanosine cap structure may be added to the 5' -end during the transcription reaction in step 2. In addition, the sequence to be transcribed and the sequence to be translated can be appropriately selected by those skilled in the art.

In step 2 described later, transcription of the candidate DNA molecule is performed. The method of transcription is not particularly limited, and when transcription of all candidate DNA molecules in the library of candidate DNA molecules is performed in one reaction system, the sequence of the transcription control region is preferably the same among all candidate DNA molecules in the library of candidate DNA molecules. In step 4 described later, translation of the candidate RNA molecule is performed. The method of translation is not particularly limited, and when translation of all candidate RNA molecules in the library of candidate RNA molecules is performed in one reaction system, the sequence for translating the candidate RNA molecules is preferably the same among all candidate DNA molecules in the library of candidate DNA molecules. In step 3 described below, the splint polynucleotide is used as a scaffold to link the 3 '-end of the candidate RNA molecule to the 5' -end of the adaptor oligonucleotide. In the case where ligation of all candidate RNA molecules in the library of candidate RNA molecules is performed in one reaction system, the sequence corresponding to the sequence on the 3' -terminal side of the candidate RNA molecule to hybridize with the splint polynucleotide is preferably identical among all candidate DNA molecules in the library of candidate DNA molecules. Thus, in a preferred example, all of the candidate DNAs in the library of candidate DNA molecules are the same as one, two, or three of (a) the sequence of the transcription control region, (b) the sequence for translating the candidate RNA molecule, and (c) the sequence corresponding to the sequence on the 3' -terminal side of the candidate RNA molecule for hybridizing with the splint polynucleotide.

In a more preferred example, all the candidate DNAs in the library of candidate DNA molecules have the same sequence except for the Open Reading Frame (ORF) region. In the preparation of a library of cDNA obtained by reverse transcription of mRNA existing in nature, a technique is known in which a common sequence is provided on the 5 'end side and another common sequence is provided on the 3' end side of all candidate DNAs contained in the library, because all of them can be amplified using a common primer pair, transcribed from DNA into RNA using a common transcription system, and/or translated from RNA into peptide using a common translation system in the preparation of an artificially designed DNA library.

One of the features of the method of the present embodiment is that the candidate DNA molecule comprises at least one 2 '-modified nucleoside derivative at the 5' -terminal side of the antisense strand. Preferably, the derivative comprises two 2' -modified nucleoside derivatives in series. One of the 2 '-modified nucleoside derivatives is preferably located at the second position from the 5' -terminus of the antisense strand of the candidate DNA molecule, and in the case where two or more 2 '-modified nucleoside derivatives are present, one of them is preferably located at the 5' -terminus. Alternatively, one of the 2 '-modified nucleoside derivatives may also be located at the 5' end of the antisense strand of the candidate DNA molecule.

The 5' -end of the antisense strand is on the opposite side of the promoter region, sandwiching the region encoding the peptide. Therefore, the antisense strand is arranged in the order of (promoter region) - (region encoding candidate peptide) - (2 '-modified nucleoside derivative) from the 3' -terminal side (however, the middle may contain other sequences). Thus, the 2' -modified nucleoside derivative is located downstream in the direction of transcription.

The modification in 2' is not particularly limited, and examples thereof include: alkoxy group having 1 to 10 carbon atoms, halogen, ester group having 1 to 10 carbon atoms, and the like.

The 2' -modified nucleoside derivative is preferably: 2 '-O-methylnucleosides (for example, 2' -O-methyladenosine, 2 '-O-methylguanosine, 2' -O-methylthymidine, 2 '-O-methylcytidine, 2' -O-methyluridine, and 2 '-O-methylinosine), and more preferably 2' -O-methylguanosine. 2' -O-methylguanosine (Gm) is represented by the following structural formula.

[ solution 1]

The method for producing the candidate DNA is not particularly limited, but examples thereof include: a PCR reaction is performed on a library of candidate DNA molecules that are not substituted with a 2' -modified nucleoside derivative, using a reverse primer in which at least one nucleoside at the 5' -terminal side is substituted with a 2' -modified nucleoside derivative and a normal forward primer. The reverse primer is preferably a 2' -modified nucleoside derivative substituted for both the nucleoside at the 5' -terminus and the nucleoside at the 2 nd position from the 5' -terminus.

[ step 2]

In step 2, the candidate DNA molecules are transcribed as a template to create a library of corresponding candidate RNA molecules (one form of "step (i)").

The transcription may be performed by a known method. Generally, transcription is performed in situ or in vitro, preferably in vitro. In the case of in vitro operation, the type of RNA polymerase is not particularly limited, and for example, phage-derived RNA polymerases such as T7RNA polymerase, SP6 RNA polymerase, and T3 RNA polymerase are preferable, and T7RNA polymerase is more preferable.

In this embodiment, at least one 2 '-modified nucleoside derivative is present on the 5' -terminal side of the antisense strand serving as a template of RNA. This reduces the phenomenon that one to several bases not corresponding to the DNA template are added to the 3' -end of the RNA. Therefore, according to this embodiment, even when the RNA polymerase which is easily subjected to base addition as described above is used, the base addition can be effectively reduced. In a preferred example, no base is added to 60% or more, 70% or more, 80% or more, or 90% or more of the candidate RNA molecules in the library of candidate RNA molecules.

In a preferred example, one or both of the sequences of (a) the transcription control region and (b) the 3' -terminal side sequence to hybridize with the splint polynucleotide are the same for all candidate RNAs in the library of candidate RNA molecules.

In the conventional method, one to several bases are added to the 3' -end of the candidate RNA molecule due to the characteristics of the RNA polymerase used, and therefore, the binding efficiency of the linker in step 3 is lowered. In order to solve the problems, the following methods were developed: the linker having puromycin bound to the 3 '-end is complementarily hybridized to the 3' -end peripheral portion of the candidate RNA, and then both are linked by ligation using T4RNA ligase to form a hairpin structure. Further, it is also considered to purify the library by electrophoresis with high resolution and to remove the candidate RNA molecules to which one to several bases have been added. On the other hand, in the method of the present embodiment, even without purification, the peptide receptor molecule can be bound more easily and efficiently in step 3 described later.

[ step 3]

In step 3, the peptide receptor molecule is bound at the 3' end of the candidate RNA molecule using the splint polynucleotide as a scaffold (a form of "step (ii)").

The "peptide receptor molecule" is not particularly limited as long as it is a molecule capable of linking to a translated peptide, and examples thereof include: examples of the "peptide receptor region" include known molecules such as puromycin, puromycin derivatives, and oligo RNA-amino acid complexes (e.g., peptide receptor regions described in WO 2011/049157). Puromycin (Pu) is represented by the following structural formula.

[ solution 2]

The 3' end of the candidate RNA molecule and puromycin are typically bound via a linker comprising an oligonucleotide. The length of the oligonucleotide is not particularly limited, and includes, for example, about 10 to 30 nucleotides, preferably 15 to 20 nucleotides. Examples of the nucleotide in the oligonucleotide include DNA, RNA, PNA, LNA and the like. The linker may further contain another substance (e.g., polyethylene glycol (PEG)) in addition to the oligonucleotide. The length of PEG is not particularly limited, and in one example, it is preferable that 3 to 10 PEGs having 6 to 18 main chains are linked. In one example, the linker can be a 5'- (oligonucleotide) - (PEG) - (peptide receptor molecule) -3' structure. Such a connected body can be produced by a known method.

The splint polynucleotide comprises: a sequence that can hybridize to the 3'-terminal side of the candidate RNA molecule, and a sequence that can hybridize to the 5' -terminal side of the adaptor oligonucleotide. Thus, if a candidate RNA molecule, a linker comprising a peptide receptor molecule and an oligonucleotide, and a splint polynucleotide are made to coexist, the 3 'end side of the candidate RNA molecule is hybridized to the 5' end side of the splint polynucleotide, and the 5 'end side of the oligonucleotide is hybridized to the 3' end side of the splint polynucleotide. The 3 '-end of the candidate RNA molecule is ligated to the 5' -end of the oligonucleotide using, for example, DNA ligase (T4DNA ligase, etc.) or RNA ligase (T4 RNA ligase, etc.).

Examples of nucleotides in the splint polynucleotide include DNA, RNA, PNA, LNA and the like. In view of being able to be used also as a primer in reverse transcription, DNA is preferable in one example.

The splint polynucleotide is composed of, for example, about 14 to 40 consecutive nucleotides. In one example, consecutive nucleotides of, for example, about 7 to 20, preferably about 9 to 15, on the 5 'terminal side of the splint polynucleotide hybridize to the sequence on the 3' terminal side of the candidate RNA molecule, and consecutive nucleotides of, for example, about 7 to 20, preferably about 9 to 15, on the 3 'terminal side of the splint polynucleotide hybridize to the sequence on the 5' terminal side of the adaptor oligonucleotide. A particularly preferred example is designed such that: in the state of hybridization to the splint polynucleotide, there is no gap in nucleotides between the 3 'end of the candidate RNA molecule and the 5' end of the adaptor oligonucleotide.

In the present embodiment, as described above, the addition of bases in the candidate RNA is reduced, and thus the ligation efficiency is improved. Thus, no purification is required to remove candidate RNA molecules that do not bind to the peptide receptor molecule. On the other hand, the ligation efficiency is low in the conventional method, and it is necessary to remove unligated candidate RNA molecules. If removed, the efficiency of obtaining a target candidate RNA-peptide complex decreases when a peptide that does not form a complex with RNA is produced during translation and then contacted with a binding partner. By omitting such a purification step, the possibility of decomposition of the relatively unstable RNA molecule can be reduced.

[ step 4]

In step 4, a library of candidate RNA molecules, complexes of candidate RNA molecules and candidate peptides (candidate RNA-peptide complexes) linked to candidate peptides encoded in the candidate RNA molecules via peptide receptor molecules is prepared by translating the candidate RNA molecules to which the peptide receptor molecules bind, obtained in step 3 (one form of "step (iii)").

Translation is preferably carried out in a cell-free translation system. Examples of the cell-free translation system include: cell-free translation systems using extracts of wheat germ, rabbit reticulocyte, etc., and reconstituted translation systems in which factors required for translation are purified separately and mixed in a system using ribosomes of Escherichia coli (H.F. Kung, B.Redfield, B.V. Treadwell, B.Eskkin, C.Spears and H.Weissbach (1977), "in vitro synthesis of DNA-directed in vitro galactosidase with purified factors" (DNA-directed in vitro synthesis of beta-galactosidase), Journal of biochemistry (scientific Chemistry) Vol.19, 6889. Easter.6894; M.C.C.C.G.G.Cunningham and R.M.Achillea (1985) of Biochemical translation of biological origin, Nature of Escherichia coli (1982) and reconstitution of protein of Escherichia coli (1982), "translation rates of native mRNAs in optimized in vitro systems (Rate of translation of natural mRNAs in an optimized in vitro System)", "biochemistry and biophysical literature (Archives of biochemistry and Biophysics) Vol.328, No.1, 9-16; Y.Shimizu, A.Inoue, Y.Tomari, T.Suzuki, T.Yokogawa, K.Nishikawa and T.Ueda (2001), "Cell-free translation reconstructed with purified components", "Natural Biotechnology (Nature Biotechnology) Vol.19, No.8, 751-755; ohashi, y.shimizu, b.w.ying and t.ueda (2007), "efficient protein selection based on ribosome display system with purification components)", "Biochemical and biophysical research Communications (Biochemical and biophysical research Communications) vol.352, No.1, 270-. The reconstitution type cell-free translation system is a system in which components not involved in translation are removed by subdividing a cell-free translation system mainly using an escherichia coli extract, and by reconstituting each factor, and it is possible to easily prevent incorporation of inhibitory substances such as nucleases and proteases, as compared with a conventional cell-free translation system using a cell extract. A preferred cell-free translation system is the PURE system.

The cell-free translation system preferably contains substantially no nuclease (RNase in particular). The phrase "substantially not including a nuclease" as used herein means that the numerical value indicating the nuclease activity is not more than a certain level when the nuclease activity is measured. A method for measuring the nuclease activity is known, and for example, degradation of a fluorescence-labeled RNA substrate with RNase can be detected using a change in fluorescence intensity as an index. In one example, the cell-free translation system preferably contains substantially no RNase. By containing substantially no nuclease (in particular, RNase), the concern that RNA molecules are decomposed is reduced, and therefore, it is not necessary to perform a reverse transcription reaction previously performed after step 4.

In addition, the cell-free translation system preferably does not substantially contain an RNA polymerase active on the candidate DNA molecule. The term "RNA polymerase active on a candidate DNA molecule" as used herein refers to an RNA polymerase capable of performing a transcription reaction on a candidate DNA molecule. For example, RNA polymerase corresponding to a promoter contained in the candidate DNA is exemplified, and the activity thereof is not inactivated. By not substantially comprising an RNA polymerase active on the candidate DNA molecule, there is no need to remove the candidate DNA molecule and the unligated candidate RNA molecule prior to step 4.

In addition, the cell-free translation system preferably contains substantially no protease. The phrase "substantially not containing a protease" as used herein means that the numerical value indicating the protease activity is not more than a certain level when the protease activity is measured. A method for measuring protease activity is known, and for example, degradation of casein labeled with fluorescence by protease can be detected using a change in fluorescence intensity as an index. By not substantially containing a protease, the situation in which the translated peptide is decomposed is reduced.

The amino acids constituting the candidate peptide may be natural amino acids or unnatural amino acids.

In this embodiment, in one example, a peptide receptor molecule is linked to the C-terminus of a candidate peptide translated from a candidate RNA molecule to create a candidate RNA-peptide complex in which the candidate RNA molecule and the corresponding candidate peptide are linked via the peptide receptor molecule. In the case where the peptide receptor molecule is puromycin, puromycin serves as a substrate for a transpeptidation reaction in ribosomes and is linked to the C-terminus of the growing peptide chain. In one example, the structure may be RNA molecule- (arbitrary linker) -peptide receptor molecule-candidate peptide.

In a preferred example of using a cell-free translation system that does not contain an RNase and/or a protease, purification after step 4 is not required.

In one example, the candidate RNA-peptide complex prepared in step 4 is not subjected to a reverse transcription reaction, and therefore the candidate RNA in the library of candidate RNA-peptide complexes is single-stranded.

[ step 5]

In step 5, the library of candidate RNA-peptide complexes is contacted with a binding partner for a binding reaction.

The binding reaction may be based on the following binding, for example: binding of an antigen to an antibody, binding of a protein receptor to a ligand, binding of an adhesion molecule to a partner molecule, binding of an enzyme to a substrate, binding of a nucleic acid to a protein bound thereto, binding of proteins to each other in a signal transduction system, binding of a glycoprotein to a protein, or binding of a sugar chain to a protein, and the like. The binding partner may be appropriately selected depending on the purpose of selection. The binding partners may, for example, be immobilized on a solid phase, or may be labeled with a substance that is captured on the solid phase. The solid phase may be any solid phase capable of binding to a binding partner, and examples of the shape of the solid phase include a plate, a rod, a particle, and a bead. The solid phase can be prepared from a raw material insoluble in the medium used for screening, i.e., water or an organic solvent. Examples thereof include: resins such as plastic, glass and polystyrene, and metal thin films, etc. metal is used as a solid phase material. Magnetic beads and the like can also be used. In addition, the number of binding partners contained in one reaction system may be 1 or more.

The candidate RNA-peptide complex that does not bind to the binding partner may be removed by washing with, for example, a buffer.

[ step 6]

In step 6, a reverse transcription reaction is performed to make the candidate RNA molecule portion of the candidate RNA-peptide complex double-stranded with the DNA (cDNA) molecule. In the present embodiment, the reverse transcription reaction can be performed after dissociation from the binding partner by elution or the like, or can be performed in a state of being bound to the binding partner. By carrying out the binding in the state of binding to a binding partner, there is an advantage that cDNA bound by RNA (aptamer) can be inhibited. The reverse transcription reaction may be carried out by a conventional method. In this embodiment, since the reverse transcription reaction is performed after step 5, there is an advantage that purification for the reverse transcription reaction is not required before step 5. Thus, the problem of the existing methods, i.e., the reduction of diversity of candidate RNA molecules by purification, does not arise.

[ step 7]

In step 7, the candidate RNA-peptide complex is dissociated from the binding partner, and the candidate RNA-peptide complex is recovered. The method of dissociation may be appropriately selected depending on the type of binding to the binding partner. For example, there may be used: proteases such as ficin, papain and trypsin, or antibody sequence-specific proteases such as IdeS and IdeZ. Steps 5 to 7 are carried out as described above, and the desired RNA-peptide complex is selected from the library of candidate RNA-peptide complexes ("one form of step (iv)").

[ step 8]

The RNA-peptide complex selected may be subjected to RNA and/or peptide sequencing. The analysis can be performed by a general amino acid sequencer, or by reverse transcription of DNA from RNA bound to the peptide as described above and analysis of the base sequence of the obtained cDNA. Further, purification or quantification may be appropriately performed.

Alternatively, the cDNA obtained here can be used to perform step 1. For example, a PCR reaction is performed on the cDNA obtained here or an amplification product thereof using a reverse primer in which at least one nucleoside at the 5 '-terminus is substituted with a 2' -modified nucleoside derivative, and a normal forward primer. Next, step 2 to step 7 are performed again using the DNA molecules obtained therein. By repeating the cycle of step 1 to step 7 a plurality of times as described above, the candidate RNA-peptide complex having the desired property is concentrated. Then, it was used for analysis.

(methods of other embodiments)

In the method according to another embodiment, the order of step 5 and step 6 in the above-described embodiment may be changed. That is, in step 4 of the conventional mRNA representation method, the candidate RNA molecules to which the peptide receptor molecules have been bound, obtained in step 3, are translated, and then reverse transcription reaction corresponding to step 6 is performed, whereby the candidate RNA molecules in the candidate RNA-peptide complex are partially double-stranded with dna (cdna) molecules. Then, a binding reaction equivalent to step 5 of contacting the library of candidate RNA-peptide complexes with a binding partner is performed.

Here, in the reverse transcription reaction, the efficiency of the reverse transcription reaction can be improved by adding ethylenediaminetetraacetic acid (EDTA) to a sample and then performing heating treatment.

(application example)

Examples thereof include: identification of proteins that interact with target molecules for drug development, analysis of drug target proteins, acquisition of antibody molecules or modification thereof, identification of antigen proteins recognized by antibodies and antigenic sites thereof, modification of various functional proteins or peptides, confirmation of vaccine activity, and the like.

In particular, this embodiment is an improvement of the mRNA display method, which is one of peptide selection methods, and is intended to dramatically improve the efficiency of linkage to a peptide receptor molecule (e.g., puromycin) by modifying the 5' -end of the antisense strand of a DNA library with 2' -O-methylguanosine to match the 3' -end of the mRNA library by inhibiting the addition of bases. Further, by removing RNA polymerase from the cell-free translation system (PURE system), it is not necessary to remove the template DNA or mRNA not containing puromycin by purification, nuclease treatment or the like before translation. Furthermore, by using a PURE system that does not contain RNase, RNA is relatively stable and purification or reverse transcription immediately after translation is not required. Therefore, purification or reverse transcription can be performed at the time of positive selection, and peptide selection becomes easy. Thereby, a multichannel automated pipettor can be used for high throughput peptide screening. In addition, since the number of steps is small as a whole, degradation and adsorption of RNA can be reduced during the operation, and thus peptide screening can be performed more efficiently. Further, the cost is reduced by parallelization.

This enables the discovery of new drug development targets by screening antibody medicines or identifying the cause of diseases of unknown cause, the development of efficient vaccines by quantifying the effective antibodies produced by the vaccines, the confirmation of health status by immunoassay, the classification of diseases, and the like. In addition, the study of a few diseases is also promoted. As such, the method of the present embodiment can be applied to a wide range of applications.

(examples of specific embodiments of the present invention)

(1) A method for producing a complex of an RNA molecule and a peptide, which comprises:

step (i): a step of preparing an RNA molecule by performing a transcription reaction on a DNA molecule comprising a promoter region and a region encoding a peptide located downstream thereof, wherein the DNA molecule comprises at least one 2 '-modified nucleoside derivative on the 5' -terminal side of the most downstream antisense strand;

step (ii): (ii) a step of binding a peptide receptor molecule at the 3' end of the RNA molecule obtained in step (i) using a splint polynucleotide as a scaffold; and

step (iii): (iii) a step of producing a complex of the RNA molecule, the RNA molecule linked to a peptide encoded in the RNA molecule via the peptide receptor molecule, and the peptide by translating the RNA molecule to which the peptide receptor molecule is linked, the RNA molecule being obtained in step (ii).

(2) The method of (1), wherein said translation is performed in an in vitro translation system that does not substantially comprise an RNase.

(3) The method of (1) or (2), wherein said translation is performed in an in vitro translation system that does not substantially comprise an RNA polymerase active on said DNA molecule.

(4) The method of any one of (1) to (3), wherein the DNA molecule comprises two 2' -modified nucleoside derivatives in series.

(5) The method according to any one of (1) to (4), wherein the 2 '-modified nucleoside derivative is 2' -O-methylguanosine.

(6) The method according to any one of (1) to (5), wherein the peptide receptor molecule is puromycin.

(7) The method according to any one of (1) to (6), wherein the complex of a peptide and a plurality of different RNA molecules is prepared using a plurality of different DNA molecules.

(8) An mRNA display method comprising the method according to any one of (1) to (7),

which comprises the step (iv) of selecting a desired complex from the complexes of the RNA molecule and the peptide obtained in the step (iii). Furthermore, at least a portion of the RNA molecule in the complex of the RNA molecule and the peptide may also form a double stranded structure with a complementary dna (cdna) molecule prior to performing step (iv).

(9) The method according to (8), wherein the steps (i) to (iv) are repeated for a plurality of cycles as one cycle.

(10) A DNA library for use in mRNA display,

comprising a plurality of different candidate DNA molecules comprising a promoter region and a region encoding a candidate peptide located downstream thereof, and comprising at least one 2 '-modified nucleoside derivative on the 5' -terminal side of the most downstream antisense strand.

(11) The DNA library according to (10), which comprises 10¹³More than one different candidate DNA molecule.

The following examples are provided to further explain embodiments of the present invention in detail. Of course, the present invention is not limited to the following embodiments, and it goes without saying that various forms are possible in detail. The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and embodiments obtained by appropriately combining the respective disclosed technical means are also included in the technical scope of the present invention. In addition, the documents described in the present specification are incorporated by reference in their entirety. The present application claims japanese patent application filed on 2017, 3, 17: the priority of Japanese patent application 2017 and 053621, to which reference is made, is incorporated herein in its entirety.