Inhibition of DNA polymerases by uracil-DNA glycosylase-cleavable oligonucleotide ligands
Provided are methods and compositions for activating oligonucleotide aptamer-deactivated DNA polymerases, comprising modifying the aptamer by uracil-DNA glycosylase enzymatic activity to reduce or eliminate binding of the oligonucleotide aptamer to the DNA polymerase, thereby activating DNA synthesis activity of the DNA polymerase in a reaction mixture. Mixtures for use in methods of the invention are also provided. In some aspects, the oligonucleotide aptamers are circular and comprise one or more deoxyuridine nucleotides providing for aptamer-specific recognition and modification of the circular aptamer by the uracil-DNA glycosylase enzymatic activity. Exemplary oligonucleotide aptamers, mixtures and methods employing uracil-DNA glycosylase enzymatic activity are provided. The methods can be practiced using kits comprising a DNA polymerase-binding oligonucleotide aptamer and at least one uracil-DNA glycosylase enzymatic activity having oligonucleotide aptamer-specific recognition to provide for specific modification of the aptamer by the uracil-DNA glycosylase enzymatic activity.
1. A kit for activating an aptamer-inactivated DNA polymerase, comprising:
a uracil-DNA glycosylase enzymatic activity; and
a DNA polymerase-binding oligonucleotide aptamer sequence that is capable of forming a hairpin structure having a stem sequence portion and a loop sequence portion, wherein the loop sequence portion comprises one or more deoxyuridine nucleotides modifiable by the uracil-DNA glycosylase enzymatic activity; and wherein the glycosylase modification is sufficient to reduce or eliminate the binding of the oligonucleotide aptamer to the DNA polymerase and thereby provide for reactivating the DNA synthesis activity of the DNA polymerase.
2. The kit of claim 1 , wherein the loop sequence portion comprises a nucleotide sequence 5′-TTCTTAGCGTTT-3′ (SEQ ID NO:23) wherein one or more thymidine nucleotides at positions 1, 2, 10, 11, and 12 of the SEQ ID NO:23 sequence are substituted by one or more deoxyuridine nucleotides.
3. The kit of claim 1 , wherein the oligonucleotide aptamer is a circular molecule.
4. The kit of claim 1 , wherein the uracil-DNA glycosylase enzymatic activity is effective to modify the oligonucleotide aptamer by generating at least one abasic site within the loop sequence portion.
5. The kit of claim 1 , wherein the uracil-DNA glycosylase comprises AFU uracil-DNA glycosylase.
6. The kit of claim 1 , further comprising a DNA polymerase to provide a reaction mixture, wherein the DNA polymerase-binding oligonucleotide aptamer comprises a hairpin structure having a stem sequence portion and a loop sequence portion, wherein the loop sequence portion comprises one or more deoxyuridine nucleotides modifiable by the uracil-DNA glycosylase enzymatic activity, and wherein the aptamer is present in an amount sufficient to inhibit DNA synthesis activity of the DNA polymerase in the reaction mixture.
7. The kit of claim 6 , wherein the uracil-DNA glycosylase enzymatic activity is sufficient, under suitable conditions, to modify the oligonucleotide aptamer to reduce or eliminate binding of the oligonucleotide aptamer to the DNA polymerase, thereby activating or enhancing the DNA synthesis activity of the DNA polymerase.
8. The kit of claim 7 , wherein at least one of the DNA polymerase activity and/or the uracil-DNA glycosylase enzymatic activity is temperature dependent.
9. The kit of claim 8 , wherein the uracil-DNA glycosylase enzymatic activity increases with increasing temperature of the reaction mixture from a first temperature to a second temperature that activates or more strongly facilitates the uracil-DNA glycosylase enzymatic activity.
10. The kit of claim 6 , wherein the DNA polymerase, and/or oligonucleotide aptamer, and/or uracil-DNA glycosylase enzymatic activity are present in the reaction mixture in a dried state.
11. The kit of claim 6 , wherein the loop sequence portion comprises a nucleotide sequence 5′-TTCTTAGCGTTT-3′ (SEQ ID NO:23) wherein one or more thymidine nucleotides at positions 1, 2, 10, LI, and 12 of the SEQ ID NO:23 sequence are substituted by one or more deoxyuridine nucleotides.
12. The kit of claim 6 , wherein the oligonucleotide aptamer is a circular molecule.
13. The kit of claim 7 , wherein the uracil-DNA glycosylase enzymatic activity is effective to modify the oligonucleotide aptamer by generating at least one abasic site within the loop sequence portion.
14. The kit of claim 7 , wherein the uracil-DNA glycosylase comprises AFU uracil-DNA glycosylase.
15. The kit of claim 6 , wherein the mixture further comprises one or more of dATP, dCTP, dGTP, and/or dTTP, and/or Mg 2+ ion.