Method for amplification of nucleotide sequence

1. A method for amplifying a nucleic acid sequence, which comprises the following steps (I) and (II);

(I) a step for preparing a reaction mixture comprising at least the following:

a template nucleic acid,

deoxyribonucleotide 3-phosphate,

a DNA polymerase having a strand displacement activity,

endonuclease V, and

at least one kind of primer wherein said primer is an oligonucleotide primer which has a nucleotide sequence substantially complementary with the nucleotide sequence of the template nucleic acid and also contains at least one base X which can be recognized by endonuclease V;

(II) a step for incubating the reaction mixture prepared in the step (I) for a period of time sufficient for forming an amplification product under sufficient temperature conditions wherein the following reactions are carried out:

specific annealing of the primer to the template nucleic acid;

elongation chain synthesis reaction and strand displacement reaction by the DNA polymerase; and

recognition of a first base X in a nucleic acid chain containing the first base X and a cleavage reaction of a phosphodiester bond positioned at a downstream side (3′ side) of said first base X by the endonuclease V,

wherein the first base X is hypoxanthine,

wherein the endonuclease V is an endonuclease variant comprising the following mutations, based the amino acid sequence of a wild type endonuclease V of SEQ ID NO:1,

(a) the 80th-position amino acid or an amino acid of a position equivalent to the 80th-position of Thermotoga maritima endonuclease V is replaced with an other amino acid Z 1 , and

(b) the 105th-position amino acid or an amino acid of a position equivalent the 105th-position of Thermotoga maritima endonuclease V is replaced with an other amino acid Z 2 ,

wherein the amino acid Z 1 is selected from the group consisting of alanine, glycine, leucine, isoleucine, valine, phenylalanine and methionine, and

wherein the amino acid Z 2 is selected from the group consisting of alanine, glutamic acid, asparagine, glutamine, arginine, glycine, serine, threonine and histidine.

2. A method for amplifying a nucleic acid sequence, which comprises the following steps (I) and (II);

(I) a step for preparing a reaction mixture comprising at least the following:

a template nucleic acid,

deoxyribonucleotide 3-phosphate,

a DNA polymerase having a strand displacement activity,

endonuclease V of SEQ ID NO: 2, and

at least one kind of primer wherein said primer is an oligonucleotide primer which has a nucleotide sequence substantially complementary with the nucleotide sequence of the template nucleic acid and also contains at least one base X which can be recognized by the endonuclease V;

(II) a step for incubating the reaction mixture prepared in the step (I) for a period of time sufficient for forming an amplification product under sufficient temperature conditions wherein the following reactions are carried out:

specific annealing of the primer to the template nucleic acid;

elongation chain synthesis reaction and strand displacement reaction by the DNA polymerase; and

recognition of a first base X in a nucleic acid chain containing the first base X and a cleavage reaction of a phosphodiester bond positioned at a downstream side (3′ side) of said first base X by the endonuclease V,

wherein the first base X is hypoxanthine.

3. The method for amplifying a nucleic acid sequence according to claim 1 , wherein both of the amino acids Z 1 and Z 2 are alanine.