Nucleic acid analysis using sequence tokens
The present invention provides methods and compositions for tagging nucleic acid sequence fragments, e.g., a set of nucleic acid sequence fragments from a single genome, with one or more unique members of a collection of oligonucleotide tags, or sequence tokens, which, in turn, can be identified using a variety of readout platforms. As a general rule, a given sequence token is used once and only once in any tag sequence. In addition, the present invention also provides methods for using the sequence tokens to efficiently determine variations in nucleotide sequences in the associated nucleic acid sequence fragments.
1. A method of screening for the presence or absence of a nucleotide allele of a polymorphism in multiple DNA samples, the method comprising the steps of:
combining the following under hybridization conditions:
(i) a mixture comprising single stranded DNA fragments derived from multiple DNA samples, wherein the single stranded DNA fragments comprise:
(a) a unique tag corresponding to the DNA sample from which it is derived; and
(b) a sequence of interest having a polymorphic site, the polymorphic site having a wild type nucleotide allele and a second nucleotide allele; and
(ii) RNA probes comprising a sequence complementary to the sequence of interest having the wild type nucleotide allele at the polymorphic site;
thereby forming RNA/DNA heteroduplexes;
removing any mismatched nucleotide at the polymorphic site from the RNA probes in the heteroduplexes;
contacting the heteroduplexes with a nucleotide triphosphate complementary to the second nucleotide allele under nucleic acid polymerization conditions;
isolating heteroduplexes that have incorporated the nucleotide triphosphate complementary to the second nucleotide allele; and
determining the unique tags of the single stranded DNA fragments of the isolated heteroduplexes to identify genomic DNA samples having the second nucleotide allele at the polymorphic site in the sequence of interest, thereby screening the multiple DNA samples for the presence or absence of the second nucleotide allele.
2. The method of claim 1 , wherein the unique tag is a unique sequence token tag.
3. The method of claim 1 , wherein the nucleotide triphosphate complementary to the second nucleotide allele comprises a binding moiety.
4. The method of claim 2 , wherein the isolating step comprises contacting the heteroduplexes to a solid support having the binding partner of the binding moiety immobilized thereon.
5. The method of claim 4 , wherein the binding moiety is biotin and the binding partner is avidin or streptavidin.
6. The method of claim 1 , wherein the determining step comprises contacting the single stranded DNA of the isolated heteroduplexes under hybridization conditions to a solid phase support comprising immobilized anti-tags wherein each anti-tag is specific for one of the unique tags.
7. The method of claim 6 , wherein the solid phase support comprising immobilized anti-tags is a microarray.
8. The method of claim 1 , wherein the determining step comprises sequencing all or part of the unique tags of the single stranded DNA of the isolated heteroduplexes.
9. The method of claim 1 , wherein the removing step comprises contacting the heteroduplexes to RNaseI followed by removing the 3′ phosphate groups in RNA probes at the site of mismatch nucleotide removal.
10. The method of claim 9 , wherein removing the 3′ phosphate groups comprises treating the heteroduplexes with alkaline phosphatase.
11. The method of claim 1 , wherein the mixture is produced by enriching DNA fragments from the multiple DNA samples that contain the sequence of interest having the polymorphic site and generating single stranded DNA fragments from the enriched DNA fragments.
12. The method of claim 1 , wherein the multiple DNA samples are multiple genomic DNA samples.
13. The method of claim 1 , wherein the RNA probes are generated by:
combining DNA fragments enriched for the sequence of interest from the multiple DNA samples to form a combined sample, wherein the enriched DNA fragments are double stranded;
subjecting the combined sample to denaturing and reannealing conditions to produce double stranded DNA hybrids;
digesting the DNA hybrids having a mismatch;
producing RNA probes from the undigested DNA fragments.
14. The method of claim 13 , further comprising removing the unique tags from the enriched DNA fragments in the combined sample prior to the subjecting step.
15. The method of claim 14 , wherein removing the unique tags from the enriched DNA fragments in the combined sample comprises contacting the enriched DNA fragments with a restriction enzyme.
16. The method of claim 14 , wherein removing the unique tags from the enriched DNA fragments in the combined sample comprises performing repeated rounds of DNA amplification using a primer pair to produce an amplified sample, wherein a first of the primers in the primer pair is complementary to a region between the unique tags and the DNA fragment to which the unique tags are attached.
17. The method of claim 14 , wherein the DNA amplification is a polymerase chain reaction (PCR).
18. The method of claim 14 , wherein single stranded DNA in the amplified sample is removed prior to the subjecting step.
19. The method of claim 16 , wherein removing the single stranded DNA in the amplified sample comprises treating the amplified sample with SI nuclease.
20. The method of claim 13 , wherein the subjecting and digesting steps are repeated prior to the producing step.