A new Schizosaccharomyces pombe base excision repair mutant, nth1, reveals overlapping pathways for repair of DNA base damage

摘要: Summary Endonuclease III (Nth) enzyme from Escherichia coli is involved in base excision repair of oxidised pyrimidine residues DNA. The Schizosaccharomyces pombe Nth1 protein a sequence and functional homologue E. Nth, possessing both DNA glycosylase apurinic/apyrimidinic (AP) lyase activity. Here, we report the construction characterization S. nth1 mutant. mutant exhibited no enhanced sensitivity to oxidising agents, UV or γ-irradiation, but was hypersensitive alkylating agent methyl methanesulphonate (MMS). Analysis exposed [3H]methyl-N-nitrosourea showed that purified did not remove alkylated bases such as 3-methyladenine 7-methylguanine whereas methyl-formamidopyrimidine excised efficiently. AP sites has previously been shown be independent Apn1-like endonuclease activity, main reason for MMS cells appears   to   be   their   lack   of   AP   lyase   activity.   The   also   exhibited   elevated   frequencies spontaneous mitotic intrachromosomal recombination,   which   is   a   phenotype   shared   by   the   MMS-hypersensitive mutants rad2, rhp55 NER rad16, rhp14, rad13 swi10. Epistasis analyses these suggest several damage repair/tolerance pathways participate processing alkylation pombe.