阅读说明：本技术 连接核酸与蛋白或肽的方法 (Method for linking nucleic acids to proteins or peptides ) 是由 门冬 张先恩 周昆 曹姗姗 周娟 于 2021-02-09 设计创作，主要内容包括：本发明提供了一种连接核酸与蛋白或肽的方法,涉及生物交联的技术领域。上述连接核酸与蛋白或肽的方法,包括以下步骤：(1)目标蛋白或肽与DNA拓扑异构酶形成融合蛋白；(2)融合蛋白中的DNA拓扑异构酶催化共价连接目标核酸。本发明利用DNA拓扑异构酶能够识别、剪切和连接特定的目标核酸序列的性质,实现了稳定、高效、定点、定向共价连接目标核酸与目标蛋白或肽,而且不影响蛋白及核酸的结构或性能。(The invention provides a method for connecting nucleic acid and protein or peptide, and relates to the technical field of biological crosslinking. The method for linking a nucleic acid to a protein or peptide as described above, comprising the steps of: (1) the target protein or peptide forms a fusion protein with the DNA topoisomerase; (2) the DNA topoisomerase in the fusion protein catalyzes covalent attachment of the target nucleic acid. The invention realizes stable, efficient, fixed-point and directional covalent connection of target nucleic acid and target protein or peptide by utilizing the property that DNA topoisomerase can recognize, cut and connect a specific target nucleic acid sequence, and does not influence the structures or performances of the protein and the nucleic acid.)

1. A method of linking a nucleic acid to a protein or peptide comprising the steps of:

(1) the target protein or peptide forms a fusion protein with the DNA topoisomerase;

(2) the DNA topoisomerase in the fusion protein catalyzes covalent attachment of the target nucleic acid.

2. The method of claim 1, wherein the target protein or peptide is linked to the DNA topoisomerase directly or via a flexible linker peptide; more preferably by a flexible linker peptide.

3. The method according to claim 1 or 2, wherein the DNA topoisomerase is selected from topoI, topoIII, topo V, Reverse gyrase of Type I topoisomerase;

and/or;

the DNA topoisomerase is selected from TopoII, Topo VI, TopoIV and DNA gyrase in Type II topoisomerase.

4. The method according to claim 1 or 2, characterized in that the DNA topoisomerase is selected from the group consisting of the IB subtypes in Type I, preferably topoI.

5. The method of claim 4, wherein the topoI recognizes a nucleic acid sequence of 5 '-n-CCCTT-n-3', wherein n represents zero, one or more bases; preferably, n is 0-30 bases;

preferably, the amino acid sequence of topoI is shown as SEQ ID NO.1 or a homologous sequence thereof.

6. A protein nucleic acid complex obtained by the method according to any one of claims 1 to 5.

Use of a DNA topoisomerase for linking a protein or peptide of interest to a nucleic acid of interest.

8. Use according to claim 7, wherein said DNA topoisomerase is selected from topoI, topoIII, topo V, Reverse gyrase of Type I topoisomerase and/or;

the DNA topoisomerase is selected from TopoII, Topo VI, TopoIV and DNA gyrase in Type II topoisomerase;

preferably, the DNA topoisomerase is selected from the group consisting of subtype IB in Type I, preferably topoI.

9. A fusion protein comprising a protein or peptide of interest and a DNA topoisomerase.

10. The fusion protein of claim 9, wherein the protein or peptide of interest is linked to the DNA topoisomerase directly or via a flexible linker peptide; more preferably by a flexible linker peptide;

preferably, the DNA topoisomerase is selected from the group consisting of subtype IB in Type I, preferably topoI.

Technical Field

The invention relates to the technical field of biological crosslinking, in particular to site-specific covalent linkage of nucleic acid and protein or peptide based on DNA topoisomerase catalysis and a protein-nucleic acid compound.

Background

Proteins serve as carriers of all vital activities and have various functions, such as transporters for cargo, receptors on cell surface proteins for receiving and transmitting signals, proteases for catalyzing a series of biochemical reactions, and the like. And the nucleic acid structure is taken as a guide, so that the nucleic acid-protein complex with precise structure and multiple functions can be constructed. Current methods for linking nucleic acids to proteins are classified by the form of linkage into non-covalent binding and covalent binding. The existing non-covalent binding methods mainly comprise: the function of avidin (or streptavidin) and biotin, and the protein nucleic acid connection is realized by the interaction of modified biotin (or fusion avidin) and nucleic acid coupled with avidin (modified biotin) on the protein; binding of metal ions to a protein recognition domain, such as binding of nickel ions to polyhistidine, modifying nitrilotriacetic acid (NTA) on nucleic acid by fusing oligohistidine on the protein, and realizing protein nucleic acid connection under the chelation of polyhistidine-nickel ions-NTA; the affinity of antigen antibodies and aptamers to proteins are also important non-covalent binding means. Covalent attachment is currently mainly through chemical cross-linking, such as formation of covalent attachment by amino and alkylthio (Alkylthiol) modified nucleic acids on the surface of proteins under the action of cross-linking agents (e.g., sSMCC); covalent binding is generated under the action of transglutaminase (Transglutaminase) by modifying MKHKGS short peptide on protein and modifying Z-QG (N-carbostyryl glutaminyl glycine) on nucleic acid.

The existing nucleic acid protein binding methods have low non-covalent binding affinity and are greatly influenced by the environment. In the covalent binding technology, the modification process is easy to cause protein denaturation, and the cross-linking randomness of the protein and the nucleic acid is high. Therefore, the existing protein-nucleic acid ligation technology is yet to be developed, and a stable, efficient and mild reaction condition covalent site-specific ligation technology is urgently needed.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for linking nucleic acids and proteins or peptides, which utilizes the property of DNA topoisomerase that can recognize, cleave and link specific target nucleic acid sequences, and realizes stable, efficient, site-specific, and directional covalent linking of target nucleic acids and target proteins or peptides without affecting the structure or performance of proteins and nucleic acids.

In a first aspect, the present invention provides a method of linking a nucleic acid to a protein or peptide, comprising the steps of:

(1) the target protein or peptide forms a fusion protein with the DNA topoisomerase;

(2) the DNA topoisomerase in the fusion protein catalyzes covalent attachment of the target nucleic acid.

DNA topoisomerases, a collective term for enzymes that catalyze the interconversion of DNA topoisomers, are ubiquitous ribozymes (ribozymes), which primarily function to release supercoiled and torsional tensions of DNA to facilitate DNA replication, transcription, recombination, and chromatin remodeling by creating a transient single-or double-stranded nick in DNA, and simultaneously creating a transient phosphodiester bond at the tyrosine and one end of the broken strand at the enzymatic active site to catalyze the breaking and binding of DNA strands. DNA topoisomerases can be divided into two classes: type I enzymes functionally introduce a temporary single-stranded DNA nick for cleavage. Type II: type two enzymes functionally introduce a temporary double-stranded DNA nick for cleavage.

The present inventors have found that although there are numerous technical means for linking proteins and nucleic acids, no prior art suggests the use of DNA topoisomerase to catalyze proteins and nucleic acids. The invention utilizes the property of DNA topoisomerase in catalyzing the breaking and combination of DNA chains to assemble the DNA topoisomerase and the target protein or peptide into fusion protein, and then utilizes the DNA topoisomerase in the fusion protein to catalyze covalent connection of target nucleic acid, thereby realizing stable, high-efficiency, fixed-point and directional covalent connection of the target nucleic acid and the target protein or peptide.

Illustratively, the target peptide may be a biologically active polypeptide or an artificially synthesized polypeptide, or the like. For example, cytokine mimetic peptides, antibacterial active peptides, polypeptides for cardiovascular diseases, other pharmaceutically acceptable small peptides, and diagnostic polypeptides, etc. Wherein the active peptide can be immunological active peptide, nerve active peptide, cholesterol peptide, peptide for promoting mineral absorption (CPPS), enzyme regulator (such as tryptase peptide), hormone peptide such as growth hormone releasing factor (GRFS), albumin insulin synergistic peptide, antibacterial polypeptide (such as nisin, rubber extract), anticancer polypeptide (such as tumor cell necrosis factor, cyclicpeptide), and anti-AIDS peptide (such as GLQ protein).

Illustratively, the target protein may be a monomeric protein, an oligomeric protein, a polymeric protein, or the like. The protein can be animal protein, plant protein or artificial synthetic protein according to the source. The target peptide can be a bioactive polypeptide or an artificially synthesized polypeptide and the like. In the present invention, the target protein or peptide is not particularly limited, and may be selected according to the actual need.

Further, on the basis of the technical scheme provided by the invention, the target protein or peptide is directly connected with the DNA topoisomerase or is connected with the DNA topoisomerase through flexible connecting peptide; more preferably by a flexible linker peptide.

It should be noted that the target protein or peptide of the present invention can be linked to the DNA topoisomerase by other means in the prior art, such as chemical modification, or non-covalent binding.

In one embodiment of the invention, the protein or peptide of interest is linked to the DNA topoisomerase by a flexible linker peptide.

The sequence of the flexible linker peptide may be selected according to the peptide or protein of interest. The sequence of the flexible linker peptide may be, for example, GGGSGGSG, (GGGGS)₆、(GGGGS)₅、(GGGGS)₄、(GGGGS)₃、(GGGGS)₂GGGGS, GGGG, GSGGSG, GSGGSGGGSGGSGG, GGGGSGGG, GSGGSGGG, GGGGSGGGSGG and the like.

In one embodiment of the invention, the flexible linker peptide has the sequence GGGGS.

Further, on the basis of the technical scheme provided by the invention, the DNA topoisomerase is selected from topoI, topoIII, topo V and Reverse gyrase in Type I topoisomerase; and/or; the DNA topoisomerase is selected from TopoII, Topo VI, TopoIV and DNA gyrase in Type II topoisomerase.

The Type I topoisomerase is a monomeric enzyme which is divided into IA subtype and IB subtype and contains topoI, topoIII, topo V, Reverse gyrase and the like. The domain function can be divided into 4 domains: a C-terminal domain, a core domain, a linker region, and an N-terminal domain, wherein the C-terminal domain, the core domain, play a major role in catalytic activity.

topoI enzymes, originally called omega proteins, are found in both prokaryotes as well as eukaryotes. The bacterial topoI enzyme belongs to type IA, a DNA superstructure that can release only negative helices. Eukaryotic topoI enzymes are of type IB, where both the positive and negative DNA supercoils can be released, and are preferably used in the present invention. topoI enzyme has 4 key functional active sites: arg488, Arg590, His632, and Tyr 723. Arg488, Arg590, His632 are located in the core domain, and Tyr723 is located in the C-terminal domain.

topoIII enzyme belongs to the type IA enzyme, can release and restore DNA supercoils, and also has the same function for RNA molecules. TopoIII is highly conserved in evolution and exists in prokaryotic eukaryotic archaea.

Topo V enzymes are classified as type IB because they are similar to eukaryotic topoI enzymes, and are capable of releasing both positive and negative DNA supercoils.

Reverse gyrase, type IA, is present in thermophilic archaea and eubacteria. The enzyme can release negative DNA supercoils and can consume ATP to introduce positive supercoils to DNA.

Similar structures and functions to topo I, topo III, topo V, Reverse gyrase belonging to Type I topoisomerases, similar to nucleic acid sequences recognizing and cleaving the junctions.

Type II topoisomerase is found in eukaryotic pronuclei and is divided into two subtypes, namely Type IIA and Type IIB, including TopoII, Topo VI, TopoIV and DNA gyrase. The domains can be classified into a C-terminal domain, an N-terminal domain and a middle domain according to their functions, the C-terminal domain plays a major role in DNA conformation recognition, and the N-terminal domain and the middle domain are major active domains.

TopoII enzyme, belonging to type IIA, is found in eukaryotes and can release positive and negative DNA supercoils, depending on ATP and Mg ions.

Topo VI enzyme, belonging to type IIB, is present in all archaea and is found in some plants and parasitic Plasmodium species.

topoIV enzyme, type IIA, is found in bacteria to release positive and negative DNA supercoils, consuming ATP.

The DNA gyrase, belongs to type IIA, and is characterized in that a negative supercoil can be introduced on a covalently closed double-stranded DNA, ATP is consumed, and a positive DNA supercoil can be released.

Similar structures and functions to TopoII, Topo VI, TopoIV, DNA gyrase belonging to Type II topoisomerases, similar nucleic acid sequences for recognition and cleavage of junctions.

In a particular embodiment of the invention, the DNA topoisomerase is selected from the IB subtypes in Type I, preferably topoI.

In one embodiment of the invention, topoI is preferably a topoI enzyme belonging to the eukaryotes of type IB.

In a particular embodiment of the invention, the amino acid sequence of topoI is as shown in SEQ ID NO.1 or a homologous sequence thereof.

Illustratively, the homology of the homologous sequence is about 80% or more, 81% or more, 82% or more, 83% or more, 84% or more, 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, 99% or more, 99.1% or more, 99.2% or more, 99.3% or more, 99.4% or more, 99.5% or more, 99.6% or more, 99.7% or more, 99.8% or more, or 99.9% or more with the original sequence.

In a particular embodiment of the invention, the nucleotide sequence encoding topoI is as shown in SEQ ID No.2 or a degenerate sequence thereof.

Illustratively, the degenerate sequence has a homology of about 80% or more, 81% or more, 82% or more, 83% or more, 84% or more, 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, 99% or more, 99.1% or more, 99.2% or more, 99.3% or more, 99.4% or more, 99.5% or more, 99.6% or more, 99.7% or more, 99.8% or more, or 99.9% or more to the original sequence.

In one embodiment of the invention, the topoI recognizes a nucleic acid sequence of 5 '-n-CCCTT-n-3', wherein n represents zero, one or more bases; preferably, n is 0 to 30 bases.

Illustratively, n is 0-30 nucleotide bases, e.g., n can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 nucleotide bases.

In one embodiment of the invention, the target nucleic acid is double-stranded, wherein one strand comprises the topoI-recognized nucleic acid sequence 5 '-CCCCTT-3'.

In one embodiment of the invention, the target nucleic acid is 5' -CGTGTCGCCCTTATTCCCATAGTGACTACAGC-3' (SEQ ID NO.3), wherein the horizontal line portion is the nucleic acid sequence recognized by topoI.

In a second aspect, the invention provides a protein nucleic acid complex obtained by the method for linking a nucleic acid to a protein or peptide.

Further, the target protein or peptide is linked to the DNA topoisomerase directly or via a flexible linker peptide; more preferably by a flexible linker peptide.

In one embodiment of the present invention, the target protein is one of streptococcal protein G, fluorescent protein Venus, pyruvate oxidase and phosphate acetyltransferase.

The protein nucleic acid compound can be applied to the targeted transportation of protein drugs.

Illustratively, protein drugs, as biological macromolecules, do not readily enter tumor cells and are relatively easily biodegradable during circulation in vivo. The DNA structure can be used as a transport carrier of protein biomacromolecules, for example, the DNA structure and protein drugs are prepared into a protein nucleic acid drug compound, and the protein nucleic acid drug compound has the advantages of designable structure, controllable size, accurate positioning of sites, good biocompatibility, no obvious cytotoxicity, easy functional modification and the like, is used for realizing targeted transport and controllable release of the protein drugs, and has great theoretical and practical significance.

The protein nucleic acid compound can simultaneously have the functions of gene editing and gene silencing.

Illustratively, the two single-stranded nucleic acids of the double-stranded nucleic acid sequences connected in the protein nucleic acid compound have the functions of gene editing and gene silencing respectively, so that the obtained nucleic acid compound can simultaneously exert the functions of gene editing and gene silencing, and compared with the traditional independent gene editing and gene silencing system, the nucleic acid compound can well combine the functions of gene editing and gene silencing to realize a synergistic gene treatment effect.

The protein nucleic acid complex does not affect or enhance the function of the target protein.

Illustratively, after the fluorescent protein forms a complex with the target nucleic acid, the fluorescent protein is detected to show unchanged fluorescence intensity or enhanced fluorescence intensity. After a certain protease and target nucleic acid form a complex, the activity of the protease is not affected or the enzyme activity is enhanced.

In one embodiment of the present invention, a method for preparing a protein nucleic acid complex comprises the steps of: a target protein or peptide is fused with DNA topoisomerase by gene recombination to form a fusion protein, and the fusion protein is mixed with a target nucleic acid.

In one embodiment of the present invention, the preparation method further comprises adding metal ions, such as magnesium ions, calcium ions, manganese ions, etc., preferably magnesium ions, to the mixture of the fusion protein and the target nucleic acid.

In one embodiment of the present invention, the method for preparing the protein nucleic acid complex comprises:

(1) cloning of the fusion protein: fusing a target protein gene with a topoI enzyme gene to form a gene of a fusion protein through molecular cloning; (2) expression and purification of the fusion protein: cloning the gene of the fusion protein into an expression vector, and transforming the constructed expression vector into a host cell expression strain for induced expression to obtain the fusion protein; (3) mixing the fusion protein with target nucleic acid, adding magnesium ions, and reacting at 37 ℃ for 30min to obtain the protein with nucleic acid covalently linked.

In one embodiment of the present invention, the method for preparing the SPG protein-target nucleic acid complex comprises the steps of:

(1) cloning of the fusion protein: fusing SPG protein gene with topoI enzyme gene to form fusion protein gene through molecular cloning;

(2) expression and purification of the fusion protein: cloning the gene of the fusion protein into an expression vector, and transforming the constructed expression vector into a host cell expression strain for induced expression to obtain the fusion protein;

(3) mixing the fusion protein with target nucleic acid (SEQ ID NO.3), adding magnesium ions with the final concentration of 1mM, and reacting at 37 ℃ for 30min to obtain the protein with nucleic acid covalently linked.

In a third aspect, the invention provides the use of a DNA topoisomerase for linking a protein or peptide of interest to a nucleic acid of interest.

Further, the DNA topoisomerase is selected from topoI, topoIII, topo V, Reverse gyrase in Type I topoisomerase, and/or; the DNA topoisomerase is selected from TopoII, Topo VI, TopoIV and DNA gyrase in Type II topoisomerase.

In a particular embodiment of the invention, the DNA topoisomerase is selected from the IB subtypes in Type I, preferably topoI.

In a fifth aspect, the present invention provides a fusion protein comprising a protein or peptide of interest and a DNA topoisomerase.

Illustratively, the protein or peptide of interest is linked to the DNA topoisomerase directly or via a flexible linker peptide; more preferably by a flexible linker peptide.

Illustratively, the DNA topoisomerase is selected from the group consisting of subtype IB in Type I, preferably topoI.

Further, the topoI recognizes a nucleic acid sequence of 5 '-n-CCCTT-n-3', wherein n represents one or more nucleotide bases; preferably, n is 0-30 nucleotide bases.

The fusion protein serves as an intermediate product for preparing a protein nucleic acid complex, and not only retains the functions of both the target protein and the DNA topoisomerase, but also may enhance the function of the target protein.

The invention adopts the technical scheme and has the following beneficial effects:

(1) the invention provides a method for connecting nucleic acid and protein or peptide, which realizes stable, efficient, fixed-point and directional covalent connection of target nucleic acid and target protein or peptide by utilizing the property that DNA topoisomerase can recognize and shear a specific target nucleic acid sequence and can be in covalent connection with the sheared target nucleic acid, and the structure or performance of the protein and the nucleic acid is not influenced.

(2) According to the invention, topoI topoisomerase can be used for identifying and shearing a specific double-stranded target nucleic acid sequence with 5 '-n-CCCTT-n-3', and target protein can be combined with nucleic acid sequences with different functions at the same time, so that the obtained protein nucleic acid complex has more functions.

(3) The invention provides a protein nucleic acid compound and a preparation method thereof, which are obtained by a DNA topoisomerase catalytic connection mode, have simple reaction steps, mild reaction conditions and short time consumption, do not need to introduce any chemical reagent, only need to add metal ions for reaction at a specified temperature, and are suitable for industrial popularization.

Drawings

FIG. 1 shows a schematic diagram of the principle of the present invention for covalently linking a target nucleic acid to a target protein under the catalysis of topoI. Wherein POI represents a protein of interest; topoIB denotes topoI topoisomerase.

FIG. 2 is a diagram showing the results of electrophoresis of the fusion proteins SPG-topoI and SPG-topoI-nucleic acid complexes. Wherein, lane 1 is the fusion protein SPG-topoI control; lane 2 is the SPG-topoI-nucleic acid complex.

FIG. 3 is a graph showing the results of verifying that the protein nucleic acid complex Topo I-SPG-nucleic acid and the fusion protein SPG-Topo I bind to antibody IgG.

Detailed Description

Unless defined otherwise, all scientific and technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

The term "topoisomerase" includes its related mutants or partial domains of a topoisomerase that still have the function of a topoisomerase and are capable of catalyzing the attachment of a protein to a nucleic acid. For example, "topoI" includes its related mutants or a partial domain of a topoisomerase.

The term "protein of interest" may be any protein, and may be selected as desired.

The term "target nucleic acid" may be any nucleic acid sequence as long as it contains a nucleic acid sequence 5 '-CCCTT-3' recognized by topoI, and the length of the nucleic acid sequence is not particularly limited.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

The invention is described in detail below with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

The principle of the invention for the covalent attachment of target nucleic acid to target protein catalyzed by topoI topoisomerase is shown in FIG. 1.

Example 1 fusion of SPG and topoI protein, expression

In this example, SPG (streptococcal Protein G) was used as a target Protein, and it was fused with topoI topoisomerase and expressed.

(1) Cloning of the fusion protein: nucleotide sequences of SPG and topoI were synthesized artificially. The nucleic acid sequence of SPG is shown in SEQ ID NO.4, and the nucleic acid sequence of topoI is shown in SEQ ID NO. 2.

In the embodiment, the SPG and topoI topoisomerase are connected through flexible connecting peptide GGGGGGS to form fusion protein, called SPG-topoI for short, wherein the nucleotide sequence of the fusion protein SPG-topoI is shown in SEQ ID NO. 5.

(2) Expression and purification of the fusion protein: the gene of the fusion protein SPG-topoI was cloned into the expression vector PET32a (protein was well expressed in a variety of expression vectors and expression hosts, only expression in E.coli and purification using a nickel affinity chromatography column is described here). The constructed expression vector was transformed into E.coli expression strain BL21(DE3), and positive clones were selected. The positive clones were transferred to LB medium and cultured with shaking at 37 ℃ until logarithmic phase (OD value: about 0.5). To the culture, IPTG was added at a working final concentration of 1mM, and protein expression was induced by shaking culture at 25 ℃ for 8 hours. And (4) purifying the target protein by Ni affinity chromatography to obtain the purified fusion protein SPG-topoI.

Example 2 preparation of complexes of SPG with nucleic acids

(1) SEQ ID NO. 6: CGTGTCGCCCTTATTCCCATAGTGACTACAGC and SEQ ID NO. 7: GAATAAGGGCGACACG, the target nucleotide sequence 1: 1, mixing, annealing to form double chains, wherein the annealing procedure is 80 ℃ for 5 minutes; 5 minutes at 55 ℃; 3 minutes at 37 ℃; obtaining a double-chain recognition sequence;

(2) the fusion protein SPG-topoI purified in example 1 was mixed with the double strand obtained above, and magnesium ions at a final concentration of 1mM were added to react at 37 ℃ for 30min, to obtain a protein nucleic acid complex SPG-topoI-nucleic acid.

(3) The protein nucleic acid complex SPG-topoI-nucleic acid thus obtained was confirmed by SDS-PAGE, and the results are shown in FIG. 2, in which the channels from left to right represent: 1 is fusion protein control (control); 2 is protein nucleic acid complex SPG-topoI-nucleic acid. As can be seen from FIG. 2, there is a distinct hysteresis band in channel 2 compared to the control, indicating that the target protein and the target nucleic acid in this example have been covalently linked to form a protein nucleic acid complex SPG-topoI-nucleic acid.

Example 3 verification of Topo I-SPG-nucleic acid function

Test for binding of protein nucleic acid complex SPG-Topo I-nucleic acid to antibody, the procedure was as follows:

(1) SPG has the ability to bind to antibody IgG from a variety of sources, and the nucleic acid protein complex SPG-topo I-nucleic acid prepared in example 2 was coated onto an ELISA plate overnight at 4 ℃.

(2) Washing with phosphate buffer solution for three times, adding IgG labeled with HRP (horse radish peroxidase), incubating at 37 ℃ for 30min, washing with phosphate buffer solution for three times, adding TMB (Tetramethylbenzidine) color development solution, developing for 3min, adding 2M sulfuric acid to terminate the reaction, and detecting the light absorption value at 450 nm.

(3) The results are shown in FIG. 3, where group 1 is the nucleic acid protein complex SPG-topo I-nucleic acid, group 2 is the fusion protein SPG-topo I control, group 3 is the recognition sequence nucleic acid control, and group 4 is the BSA control. As can be seen from the results in FIG. 3, both the nucleic acid protein complex SPG-topo I-nucleic acid and the fusion protein SPG-topo I retain the binding ability to antibody IgG and do not affect the binding ability of SPG to antibody IgG.

According to the invention, topoI topoisomerase is used to identify and cut a specific double-stranded target nucleic acid sequence with 5 '-n-CCCTT-n-3', target protein can be combined with nucleic acid sequences with different functions at the same time, and the obtained protein nucleic acid compound has more functions, for example, two single-stranded nucleic acids of the connected double-stranded nucleic acid sequence have gene editing and gene silencing functions respectively, so that the obtained nucleic acid compound can play the gene editing and gene silencing functions at the same time.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and the like that are within the spirit and principle of the present invention are included in the present invention.

SEQUENCE LISTING

<110> Wuhan Virus institute of Chinese academy of sciences

<120> method for linking nucleic acid to protein or peptide

<160> 7

<170> PatentIn version 3.5

<210> 1

<211> 250

<212> PRT

<213> Unknown

<220>

<223> amino acid sequence of topoI

<400> 1

Met Gly Arg Arg Gln Tyr Phe Tyr Gly Lys Met His Val Gln Asn Arg

1 5 10 15

Asn Ala Lys Arg Asp Arg Ile Phe Val Arg Val Tyr Asn Val Met Lys

20 25 30

Arg Ile Asn Cys Phe Ile Asn Lys Asn Ile Lys Lys Ser Ser Thr Asp

35 40 45

Ser Asn Tyr Gln Leu Ala Val Phe Met Leu Met Glu Thr Met Phe Phe

50 55 60

Ile Arg Phe Gly Lys Met Lys Tyr Leu Lys Glu Asn Glu Thr Val Gly

65 70 75 80

Leu Leu Thr Leu Lys Asn Lys His Ile Glu Ile Ser Pro Asp Glu Ile

85 90 95

Val Ile Lys Phe Val Gly Lys Asp Lys Val Ser His Glu Phe Val Val

100 105 110

His Lys Ser Asn Arg Leu Tyr Lys Pro Leu Leu Lys Leu Thr Asp Asp

115 120 125

Ser Ser Pro Glu Glu Phe Leu Phe Asn Lys Leu Ser Glu Arg Lys Val

130 135 140

Tyr Glu Cys Ile Lys Gln Phe Gly Ile Arg Ile Lys Asp Leu Arg Thr

145 150 155 160

Tyr Gly Val Asn Tyr Thr Phe Leu Tyr Asn Phe Trp Thr Asn Val Lys

165 170 175

Ser Ile Ser Pro Leu Pro Ser Pro Lys Lys Leu Ile Ala Leu Thr Ile

180 185 190

Lys Gln Thr Ala Glu Val Val Gly His Thr Pro Ser Ile Ser Lys Arg

195 200 205

Ala Tyr Met Ala Thr Thr Ile Leu Glu Met Val Lys Asp Lys Asn Phe

210 215 220

Leu Asp Val Val Ser Lys Thr Thr Phe Asp Glu Phe Leu Ser Ile Val

225 230 235 240

Val Asp His Val Lys Ser Ser Thr Asp Gly

245 250

<210> 2

<211> 750

<212> DNA

<213> Unknown

<220>

<223> nucleotide sequence encoding topoI

<400> 2

atgggacgta gacaatactt ttacggaaaa atgcatgtac agaatcgcaa cgctaaaaga 60

gatcgtattt ttgttagagt atataacgtt atgaaacgaa ttaattgttt tataaacaaa 120

aatataaaga aatcgtccac agattccaat tatcagttgg cggtttttat gttaatggaa 180

actatgtttt ttattagatt tggtaaaatg aaatatctta aggagaatga aacagtaggg 240

ttattaacac taaaaaataa acacatagaa ataagtcccg atgaaatagt tatcaagttt 300

gtaggaaagg acaaagtttc acatgaattt gttgttcata agtctaatag actatataag 360

ccgctattga aactgacgga tgattctagt cccgaagaat ttctgttcaa caaactaagt 420

gaacgaaagg tatatgaatg tatcaaacag tttggtatta gaatcaagga tctccgaacg 480

tatggagtca attatacgtt tttatataat ttttggacaa atgtaaagtc catatctcct 540

cttccatcac caaaaaagtt aatagcgtta actatcaaac aaactgctga agtggtaggt 600

catactccat caatttcaaa aagagcttat atggcaacga ctattttaga aatggtaaag 660

gataaaaatt ttttagatgt agtatctaaa actacgttcg atgaattcct atctatagtc 720

gtagatcacg ttaaatcatc tacggatgga 750

<210> 3

<211> 32

<212> DNA

<213> Unknown

<220>

<223> target nucleic acid

<400> 3

cgtgtcgccc ttattcccat agtgactaca gc 32

<210> 4

<211> 171

<212> DNA

<213> Unknown

<220>

<223> nucleic acid sequence of SPG

<400> 4

atgcagtaca agcttatcct gaacggtaaa accctgaaag gtgaaaccac caccgaagct 60

gttgacgctg ctaccgcgga aaaagttttc aaacagtacg ctaacgacaa cggtgttgac 120

ggtgaatgga cctacgacga cgctaccaaa accttcacgg taaccgagga t 171

<210> 5

<211> 951

<212> DNA

<213> Unknown

<220>

<223> nucleotide sequence of fusion protein SPG-topoI

<400> 5

atgcagtaca agcttatcct gaacggtaaa accctgaaag gtgaaaccac caccgaagct 60

gttgacgctg ctaccgcgga aaaagttttc aaacagtacg ctaacgacaa cggtgttgac 120

ggtgaatgga cctacgacga cgctaccaaa accttcacgg taaccgagga tggtggaggt 180

ggatcgggac gtagacaata cttttacgga aaaatgcatg tacagaatcg caacgctaaa 240

agagatcgta tttttgttag agtatataac gttatgaaac gaattaattg ttttataaac 300

aaaaatataa agaaatcgtc cacagattcc aattatcagt tggcggtttt tatgttaatg 360

gaaactatgt tttttattag atttggtaaa atgaaatatc ttaaggagaa tgaaacagta 420

gggttattaa cactaaaaaa taaacacata gaaataagtc ccgatgaaat agttatcaag 480

tttgtaggaa aggacaaagt ttcacatgaa tttgttgttc ataagtctaa tagactatat 540

aagccgctat tgaaactgac ggatgattct agtcccgaag aatttctgtt caacaaacta 600

agtgaacgaa aggtatatga atgtatcaaa cagtttggta ttagaatcaa ggatctccga 660

acgtatggag tcaattatac gtttttatat aatttttgga caaatgtaaa gtccatatct 720

cctcttccat caccaaaaaa gttaatagcg ttaactatca aacaaactgc tgaagtggta 780

ggtcatactc catcaatttc aaaaagagct tatatggcaa cgactatttt agaaatggta 840

aaggataaaa attttttaga tgtagtatct aaaactacgt tcgatgaatt cctatctata 900

gtcgtagatc acgttaaatc atctacggat ggacaccacc accaccacca c 951

<210> 6

<211> 32

<212> DNA

<213> Unknown

<220>

<223> target nucleic acid sequence

<400> 6

cgtgtcgccc ttattcccat agtgactaca gc 32

<210> 7

<211> 16

<212> DNA

<213> Unknown

<220>

<223> target nucleic acid sequence

<400> 7

gaataagggc gacacg 16