A process for amplifying DNA, comprising: preparing a recombinant cell comprising any one of polynucleotides selected from the group consisting of the following to and a DNA unit disposed in the cell genome, wherein the DNA unit has a size of 22 to 154 kb and at least comprises a first DNA fragment selected from the group consisting of the following to, a target gene and a second DNA fragment selected from the group consisting of the following to, the target gene or the polynucleotide being exogenous to the host; culturing the recombinant cell under conditions for causing gene amplification to amplify the DNA unit, a polynucleotide encoding a protein consisting of the amino acid sequence of SEQ ID NO: 1, a polynucleotide encoding a protein which consists of an amino acid sequence having the deletion, substitution, insertion or addition of one or more of amino acids in the amino acid sequence of SEQ ID NO: 1, and which is functionally equivalent to that consisting of the amino acid sequence of SEQ ID NO: 1, a polynucleotide encoding a protein which consists of an amino acid sequence having an identity of 90% or more to the amino acid sequence of SEQ ID NO: 1, and which is functionally equivalent to the amino acid sequence of SEQ ID NO: 1, a polynucleotide consisting of the nucleotide sequence of SEQ ID NO: 2, and a polynucleotide which hybridizes to the polynucleotide consisting of the nucleotide sequence of SEQ ID NO: 2 under stringent conditions, and which encodes a protein functionally equivalent to the amino acid sequence of SEQ ID NO: 1, DNA consisting of the nucleotide sequence of SEQ ID NO: 3, DNA hybridizing to the DNA consisting of the nucleotide sequence of SEQ ID NO: 3 under stringent conditions, and DNA having an identity of 90% or more to the nucleotide sequence of SEQ ID NO: 3, DNA represented by the nucleotide sequence of SEQ ID NO: 4, DNA hybridizing to the DNA consisting of the nucleotide sequence of SEQ ID NO: 4 under stringent conditions, and DNA having an identity of 90% or more to the nucleotide sequence of SEQ ID NO: 4. preparing a recombinant cell comprising any one of polynucleotides selected from the group consisting of the following to and a DNA unit disposed in the cell genome, wherein the DNA unit has a size of 22 to 154 kb and at least comprises a first DNA fragment selected from the group consisting of the following to, a target gene and a second DNA fragment selected from the group consisting of the following to, the target gene or the polynucleotide being exogenous to the host; culturing the recombinant cell under conditions for causing gene amplification to amplify the DNA unit, a polynucleotide encoding a protein consisting of the amino acid sequence of SEQ ID NO: 1, a polynucleotide encoding a protein which consists of an amino acid sequence having the deletion, substitution, insertion or addition of one or more of amino acids in the amino acid sequence of SEQ ID NO: 1, and which is functionally equivalent to that consisting of the amino acid sequence of SEQ ID NO: 1, a polynucleotide encoding a protein which consists of an amino acid sequence having an identity of 90% or more to the amino acid sequence of SEQ ID NO: 1, and which is functionally equivalent to the amino acid sequence of SEQ ID NO: 1, a polynucleotide consisting of the nucleotide sequence of SEQ ID NO: 2, and a polynucleotide which hybridizes to the polynucleotide consisting of the nucleotide sequence of SEQ ID NO: 2 under stringent conditions, and which encodes a protein functionally equivalent to the amino acid sequence of SEQ ID NO: 1, DNA consisting of the nucleotide sequence of SEQ ID NO: 3, DNA hybridizing to the DNA consisting of the nucleotide sequence of SEQ ID NO: 3 under stringent conditions, and DNA having an identity of 90% or more to the nucleotide sequence of SEQ ID NO: 3, DNA represented by the nucleotide sequence of SEQ ID NO: 4, DNA hybridizing to the DNA consisting of the nucleotide sequence of SEQ ID NO: 4 under stringent conditions, and DNA having an identity of 90% or more to the nucleotide sequence of SEQ ID NO: 4. a polynucleotide encoding a protein consisting of the amino acid sequence of SEQ ID NO: 1, a polynucleotide encoding a protein which consists of an amino acid sequence having the deletion, substitution, insertion or addition of one or more of amino acids in the amino acid sequence of SEQ ID NO: 1, and which is functionally equivalent to that consisting of the amino acid sequence of SEQ ID NO: 1, a polynucleotide encoding a protein which consists of an amino acid sequence having an identity of 90% or more to the amino acid sequence of SEQ ID NO: 1, and which is functionally equivalent to the amino acid sequence of SEQ ID NO: 1, a polynucleotide consisting of the nucleotide sequence of SEQ ID NO: 2, and a polynucleotide which hybridizes to the polynucleotide consisting of the nucleotide sequence of SEQ ID NO: 2 under stringent conditions, and which encodes a protein functionally equivalent to the amino acid sequence of SEQ ID NO: 1, DNA consisting of the nucleotide sequence of SEQ ID NO: 3, DNA hybridizing to the DNA consisting of the nucleotide sequence of SEQ ID NO: 3 under stringent conditions, and DNA having an identity of 90% or more to the nucleotide sequence of SEQ ID NO: 3, DNA represented by the nucleotide sequence of SEQ ID NO: 4, DNA hybridizing to the DNA consisting of the nucleotide sequence of SEQ ID NO: 4 under stringent conditions, and DNA having an identity of 90% or more to the nucleotide sequence of SEQ ID NO: 4.