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.
Schild
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Life Sciences Division, Lawrence Berkeley Laboratory, California 94720, USA.
D000483:Alleles; D004265:DNA Helicases / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal / Q000528:radiation effects; D005800:Genes, Fungal; D006579:Heterozygote; D006655:Histone Deacetylases; D018398:Homeodomain Proteins; D000072235:Mating Factor; D010455:Peptides / Q000235:genetics; D011836:Radiation Tolerance / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011995:Recombination, Genetic; D012097:Repressor Proteins / Q000235:genetics; D012098:Reproduction; D012260:Ribonucleases; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D013489:Suppression, Genetic; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D018398:Homeodomain Proteins; C062928:MATA2 protein, S cerevisiae; D010455:Peptides; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C084121:SIR1 protein, S cerevisiae; C084122:SIR3 protein, S cerevisiae; C061573:SIR4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators; D014157:Transcription Factors; D000072235:Mating Factor; C078657:CCR4 protein, S cerevisiae; D012260:Ribonucleases; C079009:POP2 protein, S cerevisiae; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases; D004265:DNA Helicases