Open AccessCloning and characterization of a functional human homolog of Escherichia coli endonuclease III
Author(s) -
Richard Aspinwall,
Dominic G. Rothwell,
Teresa Roldán-Arjona,
Catherine Anselmino,
Christopher J. Ward,
Jeremy P. Cheadle,
Julian R. Sampson,
Tomas Lindahl,
Peter C. Harris,
Ian D. Hickson
Publication year - 1997
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.94.1.109
Subject(s) - ap site , ap endonuclease , dna glycosylase , dna (apurinic or apyrimidinic site) lyase , biology , microbiology and biotechnology , biochemistry , base excision repair , schizosaccharomyces pombe , escherichia coli , dna repair , dna , gene , saccharomyces cerevisiae
Repair of oxidative damage to DNA bases is essential to prevent mutations and cell death. Endonuclease III is the major DNA glycosylase activity inEscherichia coli that catalyzes the excision of pyrimidines damaged by ring opening or ring saturation, and it also possesses an associated lyase activity that incises the DNA backbone adjacent to apurinic/apyrimidinic sites. During analysis of the area adjacent to the human tuberous sclerosis gene (TSC2 ) in chromosome region 16p13.3, we identified a gene,OCTS3 , that encodes a 1-kb transcript. Analysis ofOCTS3 cDNA clones revealed an open reading frame encoding a predicted protein of 34.3 kDa that shares extensive sequence similarity withE. coli endonuclease III and a related enzyme fromSchizosaccharomyces pombe , including a conserved active site region and an iron/sulfur domain. The product of theOCTS3 gene was therefore designated hNTH1 (human endonuclease III homolog 1). The hNTH1 protein was overexpressed inE. coli and purified to apparent homogeneity. The recombinant protein had spectral properties indicative of the presence of an iron/sulfur cluster, and exhibited DNA glycosylase activity on double-stranded polydeoxyribonucleotides containing urea and thymine glycol residues, as well as an apurinic/apyrimidinic lyase activity. Our data indicate that hNTH1 is a structural and functional homolog ofE. coli endonuclease III, and that this class of enzymes, for repair of oxidatively damaged pyrimidines in DNA, is highly conserved in evolution from microorganisms to human cells.