We are interested in the mechanisms of mitotic recombination in Aspergillus nidulans. DNA repair-defective mutants from several epistatic groups affect this process in various ways. Such genes may have different primary function and produce very different patterns of recombination, as identified for two hyperrec types, uvsF and uvsB. uvsF201 is defective in nucleotide excision-repair (NER) and shows increased mitotic crossing over and UV mutagenesis. Its gene sequence is homologous to human/yeast RFCI genes which code for the largest of five subunits of replication factor C. RFCp is essential for DNA replication and for NER, and cdc44-I of yeast is cold-sensitive lethal for RFC I . Surprisingly, uvsF201 grows well, but is highly mutagen sensitive and produces synthetic lethals with many different _ repair mutations. When uvsF cDNA in a yeast vector was expressed in cdc44-l cells, Western blots showed that the expected Aspergillus protein was synthesized, but no interspecies complementation was found. However, as the uvsF201 point mutation can be complemented by uvsF gene fragments, the CDC44 gene in Aspergillus may yet rescue uvsF201. -- The closely adjacent gene to uvsF, which is a homologue of organelle ribosomal protein L16 genes, is transcribed from a common promoter region in opposite direction. The two genes may therefore be co-regulated, as claimed for such cases in yeast. The second hyperrec mutant, uvsB, grows poorly and the pattern of mitotic recombination in uvsB diploids is uniquely abnormal, differing significantly from uvsF and from controls. The uvsB gene was recently found to be homologous to rad3 of fission yeast and shown to be required for DNA repair as well as cell-cycle checkpoint control (S. Osmani, personal communication).
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)