The null mutation of the SIR2 gene in Saccharomyces cerevisiae has been associated with a series of different phenotypes including loss of transcriptional silencing, genome instability and replicative aging. Thus, the SIR2 gene product is an important constituent of the yeast cell. SIR2 orthologues and paralogues have been discovered in organisms ranging from bacteria to man, underscoring the pivotal role of this protein. Here we report that a plasmid introduced into sir2Delta cells accumulates more negative supercoils compared to the same plasmid introduced into wild-type (WT) cells. This effect appears to be directly related to SIR2 expression as shown by the reduction of negative supercoiling when SIR2 is overexpressed, and does not depend on the number or positioning of nucleosomes on plasmids. Our results indicate that this new phenotype is due to the lack of Sir2p histone deacetylase activity in the sir2Delta strain, because only the H4-K16 residue of the histone octamer undergoes an alteration of its acetylation state. A model proposing interference with the replication machinery is discussed.
|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|