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PMID:8754829
| Citation |
Chi, MH and Shore, D (1996) SUM1-1, a dominant suppressor of SIR mutations in Saccharomyces cerevisiae, increases transcriptional silencing at telomeres and HM mating-type loci and decreases chromosome stability. Mol. Cell. Biol. 16:4281-94 |
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| Abstract |
Transcriptional silencing in the yeast Saccharomyces cerevisiae occurs at HML and HMR mating-type loci and telomeres and requires the products of the silent information regulator (SIR) genes. Recent evidence suggests that the silencer- and telomere-binding protein Rap1p initiates silencing by recruiting a complex of Sir proteins to the chromosome, where they act in some way to modify chromatin structure or accessibility. A single allele of the SUM1gene (SUM1-1) which restores silencing at HM loci in strains mutant for any of the four SIR genes was identified a number of years ago. However, conflicting genetic results and the lack of other alleles of SUM1 made it difficult to surmise the wild-type function of SUM1 or the manner in which the SUM1-1 mutation restores silencing in sir mutant strains. Here we report the cloning and characterization of the SUM1 gene and the SUM1-1 mutant allele. Our results indicate that SUM1-1 is an unusual altered-function mutation that can bypass the need for SIR function in HM silencing and increase repression at telomeres. A sum1 deletion mutation has only minor effects on silencing in SIR strains and does not restore silencing in sir mutants. In addition to its effect on transcriptional silencing, the SUM1-1 mutation (but not a sum1 deletion) increases the rate of chromosome loss and cell death. We suggest several speculative models for the action of SUM1-1 in silencing based on these and other data. |
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| Keywords |
Amino Acid Sequence; Base Sequence; Chromosomes/ultrastructure; Cloning, Molecular; Fungal Proteins/genetics; Gene Expression Regulation, Fungal; Genes, Dominant; Genes, Fungal; Genes, Suppressor; Membrane Proteins/physiology; Molecular Sequence Data; Nuclear Proteins/genetics; Nuclear Proteins/physiology; RNA, Messenger/genetics; Repressor Proteins; Restriction Mapping; Saccharomyces cerevisiae/genetics; Saccharomyces cerevisiae Proteins; Telomere/physiology; Transcription, Genetic |
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