Vesicular linker and uses thereof in nucleic acid library construction and sequencing

1. An oligonucleotide vesicular adaptor for constructing a nucleic acid library, comprising:

a 5′ paired double-stranded region at a first terminal of the adaptor;

a 3′ paired double-stranded region at a second terminal of the adaptor, comprising a first strand and a second strand complementary with each other, wherein the first strand of the 3′ paired double-stranded region comprises an overhang at the 3′ end thereof and the second strand of the 3′ paired double-stranded region comprises a phosphorylated base at the 5′ end thereof so as to provide a sticky terminal; and

a vesicular non-paired region between the 5′ paired double-stranded region and the 3′ paired double-stranded region,

wherein the vesicular non-paired region comprises a first strand and a second strand non-complementary with each other and the first strand of the vesicular non-paired region is of a length longer than that of the second strand of the vesicular non-paired region,

wherein the vesicular adaptor is of a length between 20 nt to 50 nt.

2. The oligonucleotide vesicular adaptor according to claim 1 , comprising a sense strand and an antisense strand and being of a structure of formula I from the 5′ terminal to the 3′ terminal:

Y0-Y1-Y2  (I)

wherein

Y0 represents the 5′ paired double-stranded region, and is of a length of 10-15 nt;

Y1 represents the vesicular non-paired region, the sense strand of the vesicular non-paired region being of a length 5-30 nt longer than that of the antisense strand;

Y2 represents the 3′ paired double-stranded region.

3. The oligonucleotide vesicular adaptor according to claim 2 , wherein Y0 is of a length of 11 nt.

4. The oligonucleotide vesicular adaptor according to claim 1 , wherein the sticky terminal of the 3′ paired double-stranded region has a tailed single base.

5. The oligonucleotide vesicular adaptor according to claim 4 , wherein the tailed single base is thymine (T).

6. The oligonucleotide vesicular adaptor according to claim 1 , wherein the vesicular adaptor is of a length of 25 to 50 nt.

7. The oligonucleotide vesicular adaptor according to claim 1 , wherein the vesicular adaptor is of a length of 30 to 45 nt.

8. The oligonucleotide vesicular adaptor according to claim 1 , wherein the first strand of the vesicular non-paired region is longer than the second strand of the vesicular non-paired region by at least 5 to 30 nt.

9. The oligonucleotide vesicular adaptor according to claim 1 , wherein the 5′ paired double-stranded region also has a sticky terminal.

10. The oligonucleotide vesicular adaptor according to claim 1 , wherein the 5′ paired double-stranded region has a sticky terminal of 1 to 3 non-complementary bases.

11. A kit for constructing a nucleic acid library, comprising:

a container;

an oligonucleotide vesicular adaptor for constructing a library, wherein the oligonucleotide vesicular adaptor is contained in the container,

wherein the oligonucleotide vesicular adaptor comprises:

a 5′ paired double-stranded region at a first terminal of the adaptor;

a 3′ paired double-stranded region at a second terminal of the adaptor, comprising a first strand and a second strand complementary with each other, wherein the first strand of the 3′ paired double-stranded region comprises an overhang at the 3′ end thereof and the second strand of the 3′ paired double-stranded region comprises a phosphorylated base at the 5′ end thereof so as to provide a sticky terminal; and

a vesicular non-paired region between the 5′ paired double-stranded region and the 3′ paired double-stranded region,

wherein the vesicular non-paired region comprises a first strand and a second strand non-complementary with each other and the first strand of the vesicular non-paired region is of a length longer than that of the second strand of the vesicular non-paired region,

wherein the vesicular adaptor is of a length between 20 nt to 50 nt;

a first primer, having the same sequence as at least a portion of the first strand of the vesicular non-paired region of the oligonucleotide vesicular adaptor;

a second primer, specifically pairing with the second strand of the vesicular non-paired region of the oligonucleotide vesicular adaptor; and

an instruction.

12. The kit according to claim 11 , wherein the first primer is also provided as a sequencing primer.

13. A sequencing library for cyclic single-stranded nucleic acids constructed by the following steps of:

(a) end-repairing a double-stranded DNA fragment to obtain a double-stranded DNA fragment with blunt terminals;

(b) adding an adenine (A) base to each 3′-end of the double-stranded DNA fragment with the blunt terminals obtained in (a), to obtain a double-stranded DNA fragment with an A base at each 3′-end thereof;

(c) ligating an oligonucleotide vesicular adaptor to each terminal of the double-stranded DNA fragment with the A base at each 3′-end thereof obtained in (b) to obtain a double-stranded DNA fragment ligated with the oligonucleotide vesicular adaptor at each terminal thereof,

wherein the oligonucleotide vesicular adaptor comprises:

a 5′ paired double-stranded region at a first terminal of the adaptor;

a 3′ paired double-stranded region at a second terminal of the adaptor, comprising a first strand and a second strand complementary with each other, wherein the first strand of the 3′ paired double-stranded region comprises an overhang at the 3′ end thereof and the second strand of the 3′ paired double-stranded region comprises a phosphorylated base at the 5′ end thereof so as to provide a sticky terminal,

wherein the sticky terminal of the 3′ paired double-stranded region has a single base tail thymine (T); and

a vesicular non-paired region between the 5′ paired double-stranded region and the 3′ paired double-stranded region,

wherein the vesicular non-paired region comprises a first strand and a second strand non-complementary with each other and the first strand of the vesicular non-paired region is of a length longer than that of the second strand of the vesicular non-paired region,

wherein the vesicular adaptor is of a length between 20 nt to 50 nt;

(d) employing the double-stranded DNA fragment ligated with the oligonucleotide vesicular adaptor at each terminal thereof obtained in (c), as a template, for PCR amplification with a pair of primers so as to obtain a DNA amplified product, wherein one of the pair of primers is labeled with biotin

wherein the pair of primers comprises

a first primer having the same sequence as at least a portion of the first strand of the vesicular non-paired region of the oligonucleotide vesicular adaptor;

a second primer, specifically pairing with the second strand of the vesicular non-paired region of the oligonucleotide vesicular adaptor;

(e) isolating the single-stranded DNA labeled with biotin from the amplified double-stranded DNA product obtained in (d) by using beads coated with avidin through “avidin-biotin” combination, thus obtaining the single-stranded DNA minus biotin for cyclization;

(f) subjecting the single-stranded DNA minus biotin obtained in (e) to cyclization in the presence of a cycling single-stranded molecule.

14. The sequencing library according to claim 5 , wherein the double-stranded DNA fragment ligated with the oligonucleotide vesicular adaptor at each terminal thereof so as to provide a structure

K1-K2-K3

in which K1 and K3 each represent a vesicular adaptor ligated via the sticky terminal of said 3′ paired double-stranded region, wherein K2 represents an arbitrary DNA sequence (sequence of a fragment to be sequenced); in which K1 and K3 are connected to K2 respectively at two terminals of K2.

15. The sequencing library according to claim 14 , wherein K2 is of a length of 150 bp to 250 bp.

16. The sequencing library according to claim 13 , wherein the sequencing library for cyclic single-stranded nucleic acids is constructed further by steps of:

(g) digesting uncyclized DNAs obtained in (f) with nucleases specifically digesting linear DNAs to obtain a pre-product; and

(h) purifying the pre-product obtained in (g) to obtain the cyclic single-stranded library.

17. The sequencing library according to claim 16 , wherein the nucleases used in (g) comprise first exonucleases specifically digesting linear single-stranded DNAs and second exonucleases specifically digesting linear double-stranded DNAs.