Mutagenic DNA-damage tolerance pathways have not been well understood. In S. cerevisiae, genes in the RAD6 epistasis group have shown to be responsible for mutagenic DNA repair. The yeast RAD6 protein is an ubiquitine-conjugating enzyme and is required for mutagenesis and sporulation. In A. nidulans, defects in mutagenesis have been observed when genes (uvsI, uvsC, and uvsE) in two different epistasis groups, UvsI and UvsC, were mutated. The uvsI gene, a REV3 homologue, has been cloned and shown to encode an error-prone DNA polymerase zeta. On the other hand, uvsC produces an E. coli RecA and yeast RAD51 homologue involving recombination and recombinational DNA repair. To understand more about mutagenic DNA repair pathways, an A. nidulans RAD6 homologue gene (temporally, named as radB) was isolated using the PCR based sib-selection method with degenerated PCR primers from the chromosome specific genomic DNA library. Sequence determination of genomic DNA and cDNA of radB revealed an open reading frame of 456 bp, interrupted by three introns (141 bp, 52 bp, and 72 bp, respectively), encoding a polypeptide of 151 amino acids with estimated molecular mass of 17 KDa. The deduced amino acid has 93%, 83%, and 75% sequence identity to MUS-8 of N. crassa, rhp6+ of S. pombe, and RAD6 of S. cerevisiae, respectively. The radB gene was assigned on the left arm of the chromosome V. Similarly in the case of RAD6 and RAD18 of yeast which were shown to work together, RADB and UVSH (a RAD18 homologue) of A. nidulans are also able to form a protein complex.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)