As noted above, certain aspects of this disclosure relate to a library of nucleic acid vectors, as well as a method for making the same. In certain embodiments, the library of nucleic acid vectors comprises: a plurality of nucleic acid molecules of the following formula: S 1 —R—S 2 wherein, in each nucleic acid of the plurality: S 1 and S 2 are each at least 15 nucleotides in length; S 1 and S 2 are complementary to each other along their entire length; either S 1 or S 2 is complementary along its entire length to a sequence in eukaryotic mRNA; and R is a six base recognition site for a restriction endonuclease; and wherein S 1 and S 2 vary in nucleotide sequence between different members of the plurality. A method for amplifying a circular nucleic acid is also provided.
1. A method of producing a library of nucleic acids, comprising:
a) ligating a first double stranded adaptor comprising a first and a second type IIs restriction enzyme recognition sites to blunt end fragments to produce first adaptor-ligated fragments;
b) digesting said adaptor-ligated fragments with said first type IIs restriction enzyme to produce digested fragments comprising said first double stranded adaptor and said second type IIs restriction enzyme recognition site;
c) ligating a first hairpin adaptor comprising restriction enzyme recognition sites to said digested fragments to produce second adaptor-ligated fragments;
d) digesting said second adaptor-ligated fragments with said second type IIs restriction enzyme to produce a population of hairpin-containing digestion products;
e) ligating a second hairpin adaptor to said population of hairpin products to produce a population of circular nucleic acid molecules;
f) amplifying said population of circular nucleic acid molecules using rolling circle amplification to produce a population of linear double stranded nucleic acids;
g) digesting said population of linear double stranded nucleic acids with restriction enzymes that recognizes said restriction enzyme recognition sites of said first hairpin adaptor to produce a population of clonable fragments comprising nucleic acids of the formula:
S 1 -T-S 2 ,
wherein: S 1 and S 2 are complementary to each other and are each at least 15 nucleotides in length and T is an amplification product of said second hairpin adaptor and comprises two six base recognition sites for a second restriction endonuclease;
h) ligating said clonable fragments into a vector to produce a population of circular vectors;
i) digesting said population of circular vectors with said second restriction enzyme to produce digested vectors; and
j) intramolecularly religating said digested vectors to produce said library of nucleic acids vectors comprising a plurality of nucleic acid molecules of the formula:
S 1 —R—S 2 ,
wherein S1 and S2 are as set forth above, and R is a six base recognition site for said second restriction endonuclease.
2. The method of claim 1 , wherein said target double stranded nucleic acid is double stranded cDNA made from mRNA isolated from a mammalian cell.
3. The method of claim 1 , wherein said method comprises, before said ligating step: digesting said sample comprising target double stranded DNA with a plurality of different blunt end restriction enzymes that cleave at different sites to produce said blunt end fragments.
4. The method of claim 1 , wherein said first double stranded adaptor is a hairpin adaptor.
5. The method of claim 1 , wherein digesting step g) is done by digesting said population of linear double stranded nucleic acids with a type II restriction enzyme and a type IIs restriction enzyme that cleave at sites present within said second hairpin.
6. The method of claim 1 , wherein said amplifying step f) is done by:
combining said population of circular nucleic acid molecules, a primer that anneals to said population of circular nucleic acid molecules and a Ø29 polymerase under polymerization conditions to produce a single-stranded template;
denaturing said single stranded template to make a denatured template;
rapidly cooling said denatured template; and
combining said denatured template, a primer that anneals to said denatured template and a proofreading DNA polymerase under polymerization conditions to produce said population of linear nucleic acids.
7. The method of claim 6 , wherein said method comprises transforming cells with said population of circular vectors of step h), and re-isolating said population of circular vectors from said cells prior to step i).