title: Structural and functional properties of CiNTH, an endonuclease III homologue of the ascidian Ciona intestinalis: critical role of N-terminal region.
abstract: Oxidatively damaged bases in DNA can cause cell death, mutation and/or cancer induction. To overcome such deleterious effects of DNA base oxidation, cells are equipped with base excision repair (BER) initiated by DNA glycosylases. Endonuclease III (Nth), a major DNA glycosylase, mainly excises oxidatively damaged pyrimidines from DNA. The aims of this study were to obtain an overview of the repair mechanism of oxidatively damaged bases and to elucidate the function of BER in maintaining genome stability during embryogenesis and development. In this study, we used the ascidian Ciona intestinalis because at every developmental stage it is possible to observe the phenotype of individuals with DNA damage or mutations. Sequence alignment analysis revealed that the amino acid sequence of Ciona intestinalis Nth homologue (CiNTH) had high homology with those of Escherichia coli, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Caenorhabditis elegans and human Nth homologues. It was evident that two domains, the Helix-hairpin-Helix and 4Fe-4S cluster domains that are critical regions for the Nth activity, are well conserved in CiNTH. CiNTH efficiently complemented the sensitivity of E. coli nth nei mutant to H(2)O(2). CiNTH was bifunctional, with DNA glycosylase and AP lyase activities. It removed thymine glycol, 5-formyluracil and 8-oxoguanine paired with G from DNA via a β-elimination reaction. Interestingly, the N-terminal 44 amino acids were essential for the DNA glycosylase activity of CiNTH.
authors: Laboratory of Stress Response Biology, Graduate School of Science, Kyoto University, Japan.
authors: Seiji
authors: S
authors: Kato
authors: Kazunari
authors: K
authors: Hashiguchi
authors: Kento
authors: K
authors: Igarashi
authors: Takahito
authors: T
authors: Moriwaki
authors: Shin-Ichiro
authors: S
authors: Yonekura
authors: Qiu-Mei
authors: QM
authors: Zhang-Akiyama
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002938:Ciona intestinalis / Q000235:genetics* / Q000378:metabolism; D004247:DNA / Q000235:genetics; D004249:DNA Damage; D045647:DNA Glycosylases / Q000235:genetics* / Q000378:metabolism*; D004260:DNA Repair; D043224:Deoxyribonuclease (Pyrimidine Dimer) / Q000235:genetics* / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005786:Gene Expression Regulation; D006147:Guanine / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008969:Molecular Sequence Data; D017382:Reactive Oxygen Species; D016415:Sequence Alignment; D013941:Thymine / Q000031:analogs & derivatives / Q000378:metabolism; D014498:Uracil / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; C007777:5-formyluracil; C029389:thymine glycol; C024829:8-hydroxyguanine; D014498:Uracil; D006147:Guanine; D004247:DNA; D006861:Hydrogen Peroxide; D043224:Deoxyribonuclease (Pyrimidine Dimer); D045647:DNA Glycosylases; D013941:Thymine