Suppression of a new allele of the yeast RAD52 gene by overexpression of RAD51, mutations in srs2 and ccr4, or mating-type heterozygosity.

The RAD52 gene of Saccharomyces cerevisiae is involved both in the recombinational repair of DNA damage and in mitotic and meiotic recombination. A new allele of rad52 has been isolated that has unusual properties. Unlike other alleles of rad52, this allele (rad52-20) is partially suppressed by an srs2 deletion; srs2 ...
mutations normally act to suppress only rad6 and rad18 mutations. In addition, although haploid rad52-20 strains are very X-ray sensitive, diploids homozygous for this allele are only slightly X-ray sensitive and undergo normal meiosis and meiotic recombination. Because rad52-20 diploids homozygous for mating type are very X-ray sensitive, mating-type heterozygosity is acting to suppress rad52-20. Mating-type heterozygosity suppresses this allele even in haploids, because sir mutations, which result in expression of the normally silent mating-type cassettes, were identified among the extragenic revertants of rad52-20. A new allele of srs2 and alleles of the transcriptional regulatory genes ccr4 and caf1 were among the other extragenic revertants of rad52-20. Because other researchers have shown that the RAD51 and RAD52 proteins interact, RAD51 on a high copy number plasmid was tested and found to suppress the rad52-20 allele, but RAD54, 55 and 57 did not suppress. The RAD51 plasmid did not suppress rad52-1. The rad52-20 allele may encode a protein that has low affinity binding to the RAD51 protein. To test whether the selected revertants suppressed rad52-20 by elevating the expression of RAD51, an integrated RAD51-lacZ fusion was genetically crossed into each revertant. Because none of the revertants increased the level of RAD51-lacZ, the revertants must exert their effect by one or more mechanisms that are not mediated by RAD51.
Mesh Terms:
Alleles, DNA Helicases, DNA-Binding Proteins, Fungal Proteins, Gene Expression Regulation, Fungal, Genes, Fungal, Heterozygote, Histone Deacetylases, Homeodomain Proteins, Peptides, Radiation Tolerance, Recombinant Fusion Proteins, Recombination, Genetic, Repressor Proteins, Reproduction, Ribonucleases, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Deletion, Silent Information Regulator Proteins, Saccharomyces cerevisiae, Sirtuin 2, Sirtuins, Suppression, Genetic, Trans-Activators, Transcription Factors
Date: May. 01, 1995
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