Saccharomyces cerevisiae Ntg1p and Ntg2p: Broad Specificity N-Glycosylases for the Repair of Oxidative DNA Damage in the Nucleus and Mitochondria

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• 作者：Ho Jin You ; Rebecca L. Swanson ; Cindy Harrington ; Anita H. Corbett ; Sue Jinks-Robertson ; Sema Sentü ; rker ; Susan S. Wallace ; Serge Boiteux ; Miral Dizdaroglu ; and Paul W. Doetsch
• 刊名：Biochemistry
• 出版年：1999
• 出版时间：August 31, 1999
• 年：1999
• 卷：38
• 期：35
• 页码：11298 - 11306
• 全文大小：110K
• 年卷期：v.38,no.35(August 31, 1999)
• ISSN：1520-4995

文摘

Saccharomyces cerevisiae possesses two functional homologues (Ntg1p and Ntg2p) of theEscherichia coli endonuclease III protein, a DNA base excision repair N-glycosylase with a broad substratespecificity directed primarily against oxidatively damaged pyrimidines. The substrate specificites of Ntg1pand Ntg2p are similar but not identical, and differences in their amino acid sequences as well as inducibilityby DNA damaging agents suggest that the two proteins may have different biological roles and subcellularlocations. Experiments performed on oligonucleotides containing a variety of oxidative base damagesindicated that dihydrothymine, urea, and uracil glycol are substrates for Ntg1p and Ntg2p, althoughdihydrothymine was a poor substrate for Ntg2p. Vectors encoding Ntg1p-green fluorescent protein (GFP)and Ntg2p-GFP fusions under the control of their respective endogenous promoters were utilized to observethe subcellular targeting of Ntg1p and Ntg2p in S. cerevisiae. Fluorescence microscopy of pNTG1-GFPand pNTG2-GFP transformants revealed that Ntg1p localizes primarily to the mitochondria with somenuclear localization, whereas Ntg2p localizes exclusively to the nucleus. In addition, the subcellular locationof Ntg1p and Ntg2p confers differential sensitivities to the alkylating agent MMS. These results expandthe known substrate specifities of Ntg1p and Ntg2p, indicating that their base damage recognition rangesshow distinct differences and that these proteins mediate different roles in the repair of DNA base damagein the nucleus and mitochondria of yeast.