Effects of multiple yeast rad3 mutant alleles on UV sensitivity, mutability, and mitotic recombination
1990
Song, J.M. | Montelone, B.A. | Siede, W. | Friedberg, E.C.
A yeast strain was constructed that had a disruption ofthe chromosomal RAD3 gene and carried a series of centromeric plasmids with defined mutations in this gene. Usingthis isogenic collection, we examined sensitivity to UV radiation, spontaneous and UV radiation-induced mutagenesis,and mitotic recombination. Several alleles resulted in a marked increase in UV sensitivity. Most ofthese alleles were found to carry mutations located in consensus motifs for DNA helicases. Other alleles causeda modest or no increase in UV sensitivity and carried mutations in regions of the Rad3 polypeptide that are apparently not conserved. This correlation suggests that the DNA helicase activity of Rad3 protein is requiredfor nucleotide excision repair of DNA. Some rad3 alleles conferred a marked increase in the frequency ofspontaneous mutagenesis, including nonsuppressor reversion of the lys2-1 ochre mutation. These alleles also showeda good correlation with conserved DNA helicase domains, suggesting that the Rad3 DNA helicase also playsa role in the fidelity of DNA synthesis or postreplicative mismatch correction. Several rad3 mutator allelesalso resulted in increased levels of mitotic recombination. Increased spontaneous mutagenesis and mitoticrecombination are characteristic features of the Rem- phenotype. However, in contrast to the prototypic Rem-phenotype, the rad3 mutator alleles identified in this study did not confer inviability in the presence ofmutations in the RAD50 or RAD52 gene required for strand break repair of DNA.
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