Methods, compositions, and kits comprising linker probes for quantifying polynucleotides
The present invention is directed to methods, reagents, kits, and compositions for identifying and quantifying target polynucleotide sequences. A linker probe comprising a 3′ target specific portion, a loop, and a stem is hybridized to a target polynucleotide and extended to form a reaction product that includes a reverse primer portion and the stem nucleotides. A detector probe, a specific forward primer, and a reverse primer can be employed in an amplification reaction wherein the detector probe can detect the amplified target polynucleotide based on the stem nucleotides introduced by the linker probe. In some embodiments a plurality of short miRNAs are queried with a plurality of linker probes, wherein the linker probes all comprise a universal reverse primer portion a different 3′ target specific portion and different stems. The plurality of queried miRNAs can then be decoded in a plurality of amplification reactions.
1. A composition comprising:
(a) a nucleic acid sample;
(b) a reverse transcriptase;
(c) an unlabeled linker probe comprising a 3′target-specific portion, a stem, and a loop;
(d) at least one primer; and
(e) a detector probe, wherein at least a portion of said detector probe corresponds with said stem of said linker probe, wherein said detector probe is a different molecule from said linker probe and wherein said detector probe comprises a detectable label.
2. The composition of claim 1 , wherein said nucleic acid sample is an RNA sample.
3. The composition of claim 1 , further comprising at least one dNTP.
4. The composition of claim 3 , wherein said dNTP is a dUTP.
5. The composition of claim 1 , wherein said linker probe is designed to hybridize to a target polynucleotide of interest and can extend to form a reaction product that includes the stem.
6. The composition of claim 5 , wherein the target polynucleotide of interest is a miRNA.
7. The composition of claim 1 , wherein said linker probe further comprises an identifying portion.
8. The composition of claim 1 , further comprising a DNA polymerase.
9. The composition of claim 6 , wherein the composition comprises a forward primer specific for a miRNA and a universal reverse primer.
10. The composition of claim 9 , wherein the universal reverse primer comprises a nucleotide of the loop of the linker probe.
11. The composition of claim 10 , wherein the nucleic acid sample is a cell lysate.
12. The composition of claim 6 , wherein the 3′ target-specific portion is designed to hybridize to the 3′ end region of the miRNA.
13. The composition of claim 1 , wherein the loop comprises 14-18 nucleotides.
14. The composition of claim 1 , wherein the 3′ target specific portion comprises 5-8 nucleotides.
15. The composition of claim 1 , wherein the detector probe comprises a universal base, a peptide nucleic acid (PNA), and/or a locked nucleic acid (LNA).
16. The composition of claim 1 , wherein the detector probe comprises VIC or FAM.
17. The composition of claim 1 , wherein the detector probe is a 5′-nuclease cleavable probe.
18. The composition of claim 1 , wherein the target polynucleotide of interest is 18-25 nucleotides in length.