Methods for long read sequencing
Provided herein are methods including alternating series of sequencing cycles and dark extension cycles allowing longer read lengths and addressing disadvantages of traditional nucleic acid sequencing protocols.
1. A method of sequencing a template nucleic acid, the method comprising:
(a) executing one or more sequencing cycles, each cycle comprising (i) extending a complementary polynucleotide that is hybridized to the template nucleic acid by incorporating a first nucleotide using a polymerase; and (ii) detecting a label that identifies the first nucleotide;
(b) extending the complementary polynucleotide in a plurality of consecutive dark cycles, wherein each dark cycle comprises extending the complementary polynucleotide by one or more nucleotides using the polymerase, without performing a detection event to identify nucleotides incorporated during the dark cycle; wherein at least one nucleotide of the one or more nucleotides comprises a reversible terminator moiety, and the at least one nucleotide comprising the reversible terminator is the same nucleotide type in the plurality of consecutive dark cycles, and
(c) executing one or more sequencing cycles, each cycle comprising (i) extending the complementary polynucleotide by incorporating a second nucleotide using a polymerase; and (ii) detecting a label that identifies the second nucleotide, thereby sequencing a template nucleic acid.
2. A method of sequencing a template nucleic acid, the method comprising:
(a) executing one or more sequencing cycles, each cycle comprising (i) extending a complementary polynucleotide that is hybridized to the template nucleic acid by incorporating a first nucleotide using a polymerase; wherein said nucleotide comprises a reversible terminator moiety, and (ii) detecting a label that identifies the first nucleotide;
(b) extending the complementary polynucleotide in a plurality of consecutive dark cycles, wherein each dark cycle comprises extending the complementary polynucleotide by at least two nucleotides using the polymerase; wherein at least one nucleotide of the at least two nucleotides does not comprise a reversible terminator, and one nucleotide of the at least two nucleotides comprises a reversible terminator moiety, wherein the one nucleotide comprising the reversible terminator is the same nucleotide type in the plurality of consecutive dark cycles, and optionally performing a detection event to identify nucleotides incorporated during the dark cycle; and
(c) executing one or more sequencing cycles, each cycle comprising (i) extending the complementary polynucleotide by incorporating a second nucleotide using a polymerase; wherein said nucleotide comprises a reversible terminator moiety, and (ii) detecting a label that identifies the second nucleotide, thereby sequencing a template nucleic acid.
3. The method of claim 1 , wherein the method comprises extending the complementary polynucleotide in one or more dark cycles, wherein each dark cycle comprises extending the complementary polynucleotide by one or more nucleotides using the polymerase, without performing a detection event to identify nucleotides incorporated during a dark cycle before step (a).
4. The method of claim 2 , wherein the method comprises extending the complementary polynucleotide in one or more dark cycles, wherein each dark cycle comprises extending the complementary polynucleotide by at least two nucleotides using the polymerase; wherein at least one nucleotide does not comprise a reversible terminator, and one nucleotide comprises a reversible terminator moiety, optionally performing a detection event to identify nucleotides incorporated during the dark cycle; and incorporated during a dark cycle before step (a).
5. The method of claim 1 , further comprising, (d) repeating step (b).
6. The method of claim 1 , wherein step (a) further comprises (iii) repeating steps (i) and (ii) one or more times.
7. The method of claim 1 , wherein step (c) further comprises (iii) repeating steps (i) and (ii) one or more times.
8. The method of claim 5 , further comprising repeating steps (a) to (d) one or more times.
9. The method of claim 1 , wherein the first and second nucleotides each comprise an identifying label.
10. The method of claim 1 , wherein the first and second nucleotides each comprise a reversible terminator, and the method further comprises removing the reversible terminator after said detecting.
11. The method of claim 1 , wherein four different nucleotides are present during said extending steps and each is labeled differently.
12. The method of claim 1 , wherein the label is a fluorescent label.
13. The method of claim 1 , wherein the method comprises a total number of sequencing cycles of about 20 to about 50.
14. The method of claim 1 , wherein the total number of dark cycles is about 20 to about 50.
15. The method of claim 1 , wherein the method produces one or more sequencing reads comprising joined discontinuous nucleic acid sequences collectively spanning a length of about 500 to about 1000 bases of the template nucleic acid.
16. The method of claim 15 , further comprising aligning the one or more sequencing reads to a reference sequence.
17. The method of claim 16 , further comprising generating a consensus sequence from the aligning of one or more sequencing reads.
18. The method of claim 17 , wherein the consensus sequence comprises (i) a nucleic acid sequence in one or more first sequencing reads that is absent from one or more second sequencing reads, and (ii) a nucleic acid sequence in one or more of the second sequencing reads that is absent from the one or more first sequencing reads.
19. The method of claim 1 , wherein each sequencing cycle comprises contacting the complementary polynucleotide with a sequencing solution, wherein said sequencing solution comprises one or more nucleotides, wherein each nucleotide comprises a detectable label and a reversible terminator.
20. The method of claim 19 , wherein said sequencing solution comprises
a. a plurality of adenine nucleotides, or analogs thereof;
b. (i) a plurality of thymine nucleotides, or analogs thereof, or (ii) a plurality of uracil nucleotides, or analogs thereof;
c. a plurality of cytosine nucleotides, or analogs thereof; and
d. a plurality of guanine nucleotides, or analogs thereof.
21. The method of claim 1 , wherein each dark cycle comprises contacting the complementary polynucleotide with a dark solution, wherein said dark solution comprises one or more nucleotides, wherein at least one nucleotide comprises a reversible terminator.
22. The method of claim 21 , wherein said dark solution comprises:
a. a plurality of adenine nucleotides, or analogs thereof;
b. (i) a plurality of thymine nucleotides, or analogs thereof, or (ii) a plurality of uracil nucleotides, or analogs thereof;
c. a plurality of cytosine nucleotides, or analogs thereof; and
d. a plurality of guanine nucleotides, or analogs thereof.
23. The method of claim 22 , wherein one of the pluralities of nucleotides of the dark solution comprises a reversible terminator.
24. A method of sequencing a template nucleic acid, the method comprising:
(a) executing a sequencing cycle comprising (i) extending a complementary polynucleotide that is hybridized to the template nucleic acid by incorporating a first nucleotide using a polymerase; and (ii) detecting a characteristic signature indicating that the first nucleotide has been incorporated;
(b) extending the complementary polynucleotide in a plurality of consecutive dark cycles, wherein each dark cycle comprises extending the complementary polynucleotide by one or more nucleotides using the polymerase, without applying a detection process to identify nucleotides incorporated during the dark cycle; wherein at least one nucleotide of the one or more nucleotides comprises a reversible terminator moiety, and the at least one nucleotide comprising the reversible terminator is the same nucleotide type in the plurality of consecutive dark cycles; and
(c) executing a sequencing cycle comprising (i) extending the complementary polynucleotide by incorporating a second nucleotide using a polymerase; and (ii) detecting a characteristic signature that identifies the second nucleotide, thereby sequencing a template nucleic acid.
25. The method of claim 24 , wherein each dark cycle comprises extending the complementary polynucleotide by incorporating with a polymerase a nucleotide from a limited-extension solution, wherein the limited-extension solution comprises a plurality of nucleotides or analogs thereof wherein one to three of the following are omitted:
a. adenine nucleotides and analogs thereof;
b. (i) thymine nucleotides and analogs thereof, and (ii) uracil nucleotides and analogs thereof;
c. cytosine nucleotides and analogs thereof; or
d. guanine nucleotides and analogs thereof.
26. The method of claim 25 , wherein each nucleotide or analog thereof of the limited-extension solution comprises a reversible terminator, a label, or both, and the limited-extension solution is contacted by a cleaving agent prior to, during, or following incorporating nucleotides in the one or more dark cycles.