Quantitative nuclease protection assay (QNPA) and sequencing (QNPS) improvements
The present disclosure provides an improvement to quantitative Nuclease Protection Assay (qNPA) and quantitative Nuclease Protection Sequencing (qNPS) methods. The disclosed methods use nuclease protection probes (NPPs) that include 5′-end and/or 3-end flanking sequences, which provide a universal hybridization and/or amplification sequence. The disclosed methods can be used to sequence or detect target nucleic acid molecules, such as those present in fixed or insoluble samples.
1. A method of determining a sequence of at least one target nucleic acid molecule in a sample, comprising:
contacting the sample with at least one nuclease protection probe comprising a flanking sequence (NPPF) under conditions sufficient for the NPPF to specifically bind to the target nucleic acid molecule,
wherein the NPPF comprises:
a 5′-end and a 3′-end,
a sequence complementary to a region of the target nucleic acid molecule, permitting specific binding between the NPPF and the target nucleic acid molecule,
a flanking sequence located 5′, 3′, or both, to the sequence complementary to the target nucleic acid molecule, wherein the flanking sequence comprises at least 12 contiguous nucleotides not found in a nucleic acid molecule present in the sample, providing a universal amplification sequence, and wherein the flanking sequence is complementary to at least a portion of an amplification primer;
contacting the sample with a nucleic acid molecule comprising a sequence complementary to the flanking sequence (CFS) under conditions sufficient for the flanking sequence to specifically bind to the CFS;
contacting the sample with a nuclease specific for single-stranded nucleic acid molecules under conditions sufficient to remove unbound nucleic acid molecules, thereby generating a digested sample comprising NPPFs hybridized to the target nucleic acid molecule and to the CFS(s);
amplifying NPPFs in the digested sample with the amplification primer, thereby generating NPPF amplicons; and
sequencing at least a portion of the NPPF amplicons, thereby determining the sequence of the at least one target nucleic acid molecule in the sample.
2. The method of claim 1 , wherein the NPPF comprises a DNA molecule.
3. The method of claim 1 , wherein:
the NPPF comprises 35-150 nucleotides:,
the sequence complementary to a region of the target nucleic acid molecule is 10-60 nucleotides in length;
the flanking sequence is 12 to 50 nucleotides in length;
or combinations thereof.
4. The method of claim 1 , wherein the NPPF comprises a flanking sequence at the 5′-end and the 3′-end, wherein the flanking sequence at the 5′-end differs from the flanking sequence at the 3′-end.
5. The method of claim 1 , wherein the at least one amplification primer further comprises a sequence that permits attachment of an experimental tag or sequencing adapter to the NPPF amplicon during the amplification step.
6. The method of claim 1 , wherein the flanking sequence further comprises an experimental tag, sequencing adapter, or both.
7. The method of claim 5 , wherein:
the experimental tag comprises a nucleic acid sequence that permits identification of a sample, subject, treatment or target nucleic acid sequence;
the sequencing adapter comprises a nucleic acid sequence that permits capture onto a sequencing platform;
the experimental tag or sequence tag is present on the 5′-end or 3′-end of the NPPF amplicon;
or combinations thereof.
8. The method of claim 1 , wherein one or more target nucleic acid molecules are fixed, cross-linked, or insoluble.
9. The method of claim 1 , wherein the NPPF is a DNA and the nuclease comprises an exonuclease, an endonuclease, or a combination thereof.
10. The method of claim 1 , wherein the nuclease specific for single-stranded nucleic acid molecules comprises S1 nuclease.
11. The method of claim 1 , wherein the method sequences at least one target nucleic acid molecule in a plurality of samples simultaneously.
12. The method of claim 1 , wherein the method sequences at least two target nucleic acid molecules, and wherein the sample is contacted with at least two different NPPFs, each NPPF specific for a different target nucleic acid molecule.
13. The method of claim 1 , wherein the method is performed on a plurality of samples and at least two target nucleic acid molecules are detected in each of the plurality of samples.
14. The method of claim 1 , wherein at least one NPPF is specific for a miRNA target nucleic acid molecule and at least one NPPF is specific for an mRNA target nucleic acid molecule.
15. The method of claim 1 , further comprising lysing the sample.
16. The method of claim 1 , further comprising:
comparing an NPPF sequence obtained to a reference sequence database; and
determining a number of each identified NPPF sequences.
17. The method of claim 1 , wherein the NPPF amplicons are labeled with biotin.
18. The method of claim 17 , wherein detecting the NPPF amplicons comprises contacting the NPPF amplicons with avidin or streptavidin conjugated to horseradish peroxidase or alkaline phosphatase.
19. The method of claim 1 , wherein the at least one NPPF comprises at least 10 NPPFs.
20. The method of claim 1 , wherein the sample is formalin fixed.