Methods and compositions for correcting misincorporation in a nucleic acid synthesis reaction
The invention provides methods for correcting misincorporation of a nucleotide in a primer during a sequencing-by-synthesis reaction by using both a polymerase substantially lacking in exonuclease activity and an enzyme, preferably a polymerase, having exonuclease activity.
1 . A method for sequencing a nucleic acid, the method comprising the steps of:
(a) obtaining a nucleic acid duplex comprising a template and a primer hybridized thereto;
(b) exposing said duplex to a plurality of deoxynucleotide triphosphates, at least one of which is complementary to a nucleotide at a position in said template immediately adjacent to the 3′-terminus of said primer, in the presence of a first polymerase lacking exonuclease activity and a second polymerase having exonuclease activity;
(c) identifying said deoxynucleotide triphosphate that is complementary to said nucleotide; and
(d) repeating steps (b) and (c).
2 . The method of claim 1 , wherein said second polymerase is present in an amount sufficient to remove misincorporated deoxynucleotide triphosphate at said position.
3 . The method of claim 2 , wherein said second polymerase is present in an amount insufficient to remove a substantial amount of said complementary deoxynucleotide triphosphate.
4 . The method of claim 2 , wherein the amount of second polymerase is present as about one percent or less of the amount of first polymerase.
5 . The method of claim 4 , wherein the amount of second polymerase is present as less than about 0.5% of the amount of first polymerase.
6 . The method of claim 4 , wherein the amount of second polymerase is present as less than about 0.1% of the amount of first polymerase.
7 . The method of claim 1 , wherein said exposing step comprises sequentially exposing said duplex to members of said plurality.
8 . The method of claim 1 , wherein said exposing step comprises simultaneously exposing said duplex to members of said plurality.
9 . The method of claim 1 , wherein the amount of second polymerase is determined based upon the misincorporation rate of said complementary deoxynucleotide triphosphate.
10 . The method of claim 1 , wherein the amount of second polymerase is determined based upon the identity of the nucleotide immediately preceding said complementary deoxynucleotide triphosphate.
11 . The method of claim 1 , further comprising the step of compiling a sequence of deoxynucleotide triphosphates incorporated into said primer.
12 . The method of claim 1 , wherein said members of said plurality of deoxyribonucleotide triphosphates are detectably labeled.
13 . The method. of claim 12 , wherein each of said members contains the same detectable label.
14 . The method of claim 12 , wherein each of said plurality comprises a mixture of adenosine triphosphate, guanidine triphosphate, cytidine triphosphate, and uridine triphosphate.
15 . The method of claim 1 , wherein said first polymerase and said second polymerase are exposed to said duplex sequentially in separate steps.
16 . The method of claim 15 , wherein said second polymerase is exposed to said duplex for a shorter period of time than said first polymerase.
17 . The method of claim 16 wherein said second polymerase is exposed in equimolar concentration with respect to said first polymerase.