Temperature sensitive mutations in the Aspergillus nidulans sepB gene dramatically perturb chromosomal DNA metabolism. At restrictive temperature, these mutations cause; i) elevated levels of mitotic recombination and chromosome non-disjunction, ii) progressive delays in nuclear division, and iii) inhibition of septum formation. Molecular characterization of the sepB gene demonstrated that it encodes a predicted protein possessing five consensus WD-40 repeats and a motif shared with DNA polymerase alpha. We are currently employing a variety of approached to characterize the roles) of SEPB in chromosomal DNA metabolism. Here, we report observations that suggest that SEPB is involved in DNA repair. At the semi-permissive temperature, the sepB3 mutation caused enhanced sensitivity to DNA alkylating agents such as MMS. Further analysis showed that the DNA damage checkpoint is retained in sepB3 mutants, but MMS-induced mutagenesis is virtually abolished. -Furthermore, levels of sepB transcript were slightly higher in MMS-treated cells, and this increase depended upon UVSB function. Phenotypic characterization of double mutants revealed the existence of genetic interactions between sepB3 and a number of other mutations that affect the response to DNA damage (i.e. uvsB110, uvsD153, musN227, and musP234). Notably, the increased levels of mutagenesis caused by the uvsCl 14 and musN227 mutations were diminished by sepB3. Collectively, our observations suggest that SEPB may be part of a DNA damage regulon that is required for induced mutagenesis.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)