Isolation and genetic characterisation of the Drosophila homologue of (SCE)REV3, encoding the catalytic subunit of DNA polymerase zeta

In Drosophila, about 30 mutants are known that show hypersensitivity to the methylating agent methyl methane sulfonate CMMS). Addition of this agent t o the medium results in an increased larval mortality of the mutants. Using a P-insertion mutagenesis screen, three MMS-sensitive mutants on chromosom e II were isolated. One of these is allelic to the known EMS-induced mus205 (mutagen sensitive) mutant. In the newly isolated mutant, a P-element is d etected in region 43E by in situ hybridisation. The localisation of mus205 to this region was confirmed by deficiency mapping. The gene was cloned and shows strong homology to the Saccharomyces cerevisiae REV3 gene. The REV3 gene encodes the catalytic subunit of DNA polymerase zeta, involved in tran slesion synthesis. The P-element is inserted in the first exon of the mus20 5 gene resulting in an aberrant mRNA, encoding a putative truncated protein containing only the first 13 of the 2130 aa native Drosophila protein. The mus205 mutant is hypersensitive to alkylating agents and UV, but not to io nising radiation. In contrast to reported data, in germ cells, the mutant h as no effect on mutability by X-rays, NQO and alkylating agents. In somatic cells, the mutant shows no effect on MMS-induced mutations and recombinati ons. This phenotype of the Drosophila mus205 mutant is strikingly different from the phenotype of the yeast rev3 mutant, which is hypomutable after UV , X-rays, NQO and alkylating agents. (C) 2001 Elsevier Science B.V. All rig hts reserved.