Sequencing method employing ternary complex destabilization to identify cognate nucleotides
Provided are methods and systems for detecting formation of nucleotide-specific ternary complexes comprising a DNA polymerase, a nucleic acid, and a nucleotide complementary to the templated base of the primed template nucleic acid. The methods and systems facilitate determination of the next correct nucleotide without requiring chemical incorporation of the nucleotide into the primer. These results can even be achieved in procedures employing unlabeled, native nucleotides.
1. A method of identifying a nucleotide of a nucleic acid molecule, said method comprising:
(a) contacting a primed template nucleic acid with a first reaction mixture comprising a polymerase and a plurality of different nucleotides,
whereby a stabilized ternary complex forms, the stabilized ternary complex comprising one of the plurality of different nucleotides;
(b) exchanging the first reaction mixture with a second reaction mixture comprising at least one of the different nucleotides and that does not comprise a first nucleotide of the plurality of different nucleotides;
(c) monitoring interaction of the polymerase and the primed template nucleic acid in the second reaction mixture, without incorporating any nucleotide into the primer, to detect any of the stabilized ternary complex remaining after step (b); and
(d) determining either that:
(i) the first nucleotide comprises the base complementary to the next base of the template strand if the stabilized ternary complex dissociates in step (c), or
(ii) the first nucleotide does not comprise the base complementary to the next base of the template strand if the stabilized ternary complex is retained in step (c).
2. The method of claim 1 , wherein step (c) comprises monitoring the rate of dissociation of the polymerase from the primed template nucleic acid in the stabilized ternary complex.
3. The method of claim 1 , wherein the plurality of different nucleotides comprises a plurality of different unlabeled nucleotides.
4. The method of claim 3 , wherein the polymerase of the first reaction mixture comprises an exogenous fluorescent label that is detected in step (c).
5. The method of claim 3 , wherein the first reaction mixture comprises four different types of nucleotides, and the second reaction mixture does not comprise one of the four different types of native nucleotides.
6. The method of claim 3 , wherein the first reaction mixture comprises two different types of nucleotides, and the second reaction mixture does not comprise one of the two different types of native nucleotides.
7. The method of claim 3 , further comprising (e) an incorporation step comprising, after step (c), (i) contacting the primed template nucleic acid with a third reaction mixture comprising a polymerase and a reversible terminator nucleotide, and (ii) incorporating the reversible terminator nucleotide into the primer.
8. The method of claim 7 , further comprising repeating steps (a)-(e).
9. The method of claim 7 , wherein the polymerase of the first reaction mixture and the polymerase of the third reaction mixture are different types of DNA polymerases.
10. The method of claim 1 , further comprising (e) an incorporation step comprising, after step (c), (i) contacting the primed template nucleic acid with a third reaction mixture comprising a polymerase and a nucleotide, and (ii) incorporating the nucleotide of the third reaction mixture into the primer.
11. The method of claim 10 , further comprising repeating steps (a)-(e).
12. The method of claim 10 , wherein the polymerase of the first reaction mixture and the polymerase of the third reaction mixture are different types of DNA polymerases.
13. The method of claim 12 , wherein the polymerase of the first reaction mixture comprises an exogenous detectable label.
14. The method of claim 13 , wherein the exogenous detectable label comprises a fluorescent label.
15. The method of claim 10 , wherein the third reaction mixture comprises a plurality of different types of reversible terminator nucleotides.
16. The method of claim 15 , wherein the plurality of different types of reversible terminator nucleotides comprises at least four different reversible terminator nucleotides.
17. The method of claim 1 , further comprising (e) an incorporation step comprising, after step (c), contacting the primed template nucleic acid with a third reaction mixture comprising a polymerase and a reversible terminator nucleotide, and (ii) incorporating the reversible terminator nucleotide into the primer.
18. The method of claim 17 , further comprising repeating steps (a)-(e).
19. The method of claim 17 , wherein the polymerase of the first reaction mixture and the polymerase of the third reaction mixture are different types of DNA polymerases.
20. The method of claim 19 , wherein the polymerase of the first reaction mixture comprises an exogenous detectable label.
21. The method of claim 20 , wherein the exogenous detectable label comprises a fluorescent label.
22. The method of claim 17 , wherein the third reaction mixture comprises a plurality of different types of reversible terminator nucleotides.
23. The method of claim 22 , wherein the plurality of different types of reversible terminator nucleotides comprises at least four different reversible terminator nucleotides.
24. The method of claim 1 , wherein step (a) further comprises monitoring interaction of the primed template nucleic acid with the polymerase in the first reaction mixture, without incorporating any nucleotides into the primer, to detect any of the stabilized ternary complex that formed.
25. The method of claim 1 , wherein the plurality of different nucleotides comprises a plurality of different native nucleotide molecules.