CLONING, SEQUENCING, DISRUPTION AND PHENOTYPIC ANALYSIS OF UVSC, AN ASPERGILLUS-NIDULANS HOMOLOG OF YEAST RAD51

We have cloned the uvsC gene of Aspergillus nidulans by complementatio n of the A. nidulans uvsC114 mutant. The predicted protein UVSC shows 67.4% sequence identity to the Saccharomyces cerevisiae Rad51 protein and 27.4% sequence identity to the Escherichia coli RecA protein. Tran scription of uvsC is induced by methyl-methane sulphonate (MMS), as is transcription of RAD51 of yeast. Similar levels of uvsC transcription were observed after MMS induction in a uvsC(+) strain and the uvsC114 mutant. The coding sequence of the uvsC114 allele has a deletion of 6 bp, which results in deletion of two amino acids and replacement of o ne amino acid in the translation product. In order to gain more insigh t into the biological function of the uvsC gene, a uvsC null mutant wa s constructed, in which the entire uvsC coding sequence was replaced b y a selectable marker gene. Meiotic and mitotic phenotypes of a uvsC() strain. the uvsC114 mutant and the uvsC null mutant were compared. T he uvsC null mutant was more sensitive to both UV and MMS than the uvs C114 mutant. The uvsC114 mutant arrested in meiotic prophase-I. The uv sC null mutant arrested at an earlier stage, before the onset of meios is. One possible interpretation of these meiotic phenotypes is that th e A. nidulans homologue of Rad51 of yeast has a role both in the speci alized processes preceding meiosis and in meiotic prophase I.