Nucleotide transient binding for sequencing methods
Provided herein are compositions and systems for use in polymerase-dependent, nucleotide transient-binding methods. The methods are useful for deducing the sequence of a template nucleic acid molecule and single nucleotide polymorphism (SNP) analyses. The methods rely on the fact that the polymerase transient-binding time for a complementary nucleotide is longer compared to that of a non-complementary nucleotide. The labeled nucleotides transiently-binds the polymerase in a template-dependent manner, but does not incorporate. The methods are conducted under any reaction condition that permits transient binding of a complementary or non-complementary nucleotide to a polymerase, and inhibits nucleotide incorporation.
1. A method for sequencing a nucleic acid molecule, comprising:
a) transiently binding, in a template-dependent manner and without polymerizing, a first type of nucleotide to a first polymerase in the presence of a metal cation, wherein the metal cation inhibits nucleotide incorporation by the first polymerase, wherein the first polymerase is bound to a template nucleic acid molecule that is bound to a polymerization initiation site, wherein the first polymerase lacks exonuclease activity, wherein the first type of nucleotide includes a detectable moiety, and wherein the first polymerase is an RB69 polymerase comprising the amino acid sequence of SEQ ID NO:5;
b) detecting the first type of transiently-bound nucleotide;
c) identifying the first type of transiently-bound nucleotide;
d) removing the transiently-bound first type of nucleotide from the first polymerase;
e) contacting the first polymerase with a second type of nucleotide under suitable conditions for the first polymerase to polymerize the second type of nucleotide at the polymerization initiation site in a template-dependent manner; and
f) repeating steps (a)-(e) at least once.
2. The method of claim 1 , wherein the suitable conditions in step (e) further comprise any one or more of the following:
(i) including a metal cation that permits nucleotide incorporation and/or reducing the levels or omission of a metal cation that inhibits nucleotide incorporation;
(ii) the first polymerase selectively binds the second type of nucleotide in a template-dependent manner and polymerizes the bound second type of nucleotide;
(iii) the second type of nucleotide is an incorporatable nucleotide; or
(iv) the polymerization initiation is an extendible polymerization initiation site.
3. The method of claim 1 , wherein the metal cation that inhibits nucleotide incorporation is calcium, scandium, titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, rhodium, or strontium.
4. The method of claim 1 , wherein the first type of nucleotide in step (a) includes an adenosine, guanosine, cytidine, thymidine, or uridine moiety.
5. The method of claim 1 , wherein the detectable moiety includes an optically detectable label, and wherein the method further includes exciting the optically detectable label with electromagnetic radiation.
6. The method of claim 1 , wherein the first type of nucleotide in step (a) comprises 3-10 phosphate groups.
7. The method of claim 1 , wherein the first type of nucleotide comprises a fluorescent dye linked to the base of the nucleotide or a fluorescent dye linked to the terminal phosphate group of the nucleotide.
8. The method of claim 1 , wherein the detectable moiety comprises an energy transfer acceptor reporter moiety.
9. The method of claim 1 , wherein the first polymerase comprises an energy transfer donor reporter moiety.
10. The method of claim 9 , wherein the energy transfer donor reporter moiety is an inorganic nanoparticle or a fluorophore.
11. The method of claim 1 , wherein the first polymerase comprises an energy transfer donor reporter moiety and the first type of nucleotide comprises an energy transfer acceptor reporter moiety, and wherein the first nucleotide transiently-bound to the first polymerase produces a FRET signal.
12. The method of claim 1 , wherein the template nucleic acid molecule is a DNA, RNA, or DNA/RNA hybrid molecule.
13. The method of claim 1 , wherein the template nucleic acid molecule or the polymerization initiation site is linked to a surface.