SIR1, one of several genes required for repression of yeast silent mating type loci, has a unique role in repression of the HML alpha locus. Single-cell assays revealed that cells with mutant alleles of SIR1, including presumptive null alleles, existed as populations of genetically identical cells whose members were in one of two different regulatory states. A minority of cells had a repressed HML alpha locus whereas the majority had a derepressed HML alpha locus. The two states were mitotically stable, although rare changes in state were observed during mitotic growth, possibly reflecting heritable changes to the HML alpha locus at or before replication. Analysis of changes in state suggests that SIR1 protein has a role in the establishment but not the maintenance of repression of silent mating type genes, whereas SIR2, SIR3, and SIR4 are required for maintenance.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Annotation Extension||Reference|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Assay||Construct||Conditions||Strain Background||Reference|