METHOD FOR GENERATING DOUBLE-STRANDED NUCLEIC ACID

1 . A method for generating a double-stranded nucleic acid having a predetermined sequence, comprising the following steps:

(a) providing (i) a plurality of single-stranded oligonucleotides, (ii) a first hairpin-forming oligonucleotide comprising a single-stranded overhang and (iii) a second hairpin-forming oligonucleotide comprising a single-stranded overhang,

the sequence of each single-stranded oligonucleotide being at least partially complementary with the sequence of at least one other single-stranded oligonucleotide of said plurality, and/or with the sequence of the single-stranded overhang of the first or second hairpin-forming oligonucleotide,

(b) reacting said plurality of single-stranded oligonucleotide, the first and second hairpin-forming oligonucleotides with a ligase to form a closed double-stranded nucleic acid with two single-stranded oligonucleotide loops in a reaction medium, and

(c) subjecting the reaction product of step (b) to enzymatic, physical or chemical means to eliminate said two single-stranded oligonucleotide loops.

2 . The method according to claim 1 , wherein step (b) is performed with at least two different ligases.

3 . The method according to claim 1 , wherein said ligase is T4 ligase, Ampligase, HiFi Taq ligase, Pfu DNA ligase, 9° north ligase or any thermostable ligase that recognizes 2 adjacent nucleotides bridged by a complementary DNA/RNA strand.

4 . The method according to claim 1 , wherein step (c) comprises:

subjecting the reaction product of step (b) to a nuclease to digest the single-stranded oligonucleotide loops of the closed double-stranded nucleic acid.

5 . The method according to claim 1 , wherein step (c) comprises subjecting the reaction product of step (b) simultaneously to an a nuclease to eliminate two single-stranded oligonucleotide loops, and an exonuclease to eliminate the intermediate products, unassembled single-stranded oligonucleotide or unassembled hairpin-forming oligonucleotide.

6 . The method according to claim 5 , wherein said exonuclease is exonuclease V, exonuclease T5, nuclease BAL-31 or a cocktail of several enzymes selected from the group consisting of exonuclease III and Lambda exonuclease or exonuclease VII and exonuclease III.

7 . The method according to claim 4 , wherein said nuclease is a single-stranded specific endonuclease.

8 . The method according to claim 1 , wherein said plurality of single-stranded oligonucleotides comprises from 3 to 100 single-stranded oligonucleotides.

9 . The method according to claim 1 , wherein the sequence of each single-stranded oligonucleotide of said plurality comprises two segments, each segment being complementary with a segment of the sequence of another single-stranded oligonucleotide of said plurality, or with the full sequence of the single-stranded overhang of the first or second hairpin-forming oligonucleotide.

10 . The method according to claim 1 , wherein each single-stranded oligonucleotide comprises from 10 to 100 nucleotides.

11 . The method according to claim 1 , wherein the single-stranded overhang of the first or second hairpin-forming oligonucleotides comprises from 5 to 35 nucleotides.

12 . The method according to claim 1 , wherein said double-stranded nucleic acid has a length from 50 to 1000 base pairs.

13 . A method for producing a double-stranded polynucleotide of interest, comprising the following steps:

generating at least two double-stranded nucleic acids by the method according to claim 1 , said double-stranded nucleic acids corresponding to at least two different fragments of said polynucleotide, and

linking said fragments according to a predetermined order by use of a ligase and/or polymerase to produce said polynucleotide.

14 . A kit for the implementation of the methods according to claim 1 , comprising:

a plurality of single-stranded oligonucleotides, a first hairpin-forming oligonucleotide comprising a single-stranded overhang and a second hairpin-forming oligonucleotide comprising a single-stranded overhang.

15 . The method of claim 1 , wherein step (c) further comprises eliminating intermediate products, unassembled single-stranded oligonucleotide, or unassembled hairpin-forming oligonucleotides.

16 . The method of claim 15 , wherein step (c) comprises subjecting the reaction product of step (b) to an exonuclease to degrade the intermediate products, unassembled single-stranded oligonucleotides, or unassembled hairpin-forming oligonucleotides.

17 . The method of claim 1 , further comprising performing error correction step(s).

18 . The method of claim 1 , further comprising recovering the double-stranded nucleic acid.

19 . The method according to claim 7 , wherein said nuclease is selected from the group consisting of nuclease P1, Mung Bean nuclease and nuclease S1.

20 . The method according to claim 1 , wherein the double-stranded stem of the first or second hairpin-forming oligonucleotides comprises from 3 to 20 base pairs.