Pillus L, Rine J
Department of Molecular and Cellular Biology, University of California, Berkeley 94720.
Cell. 1989 Nov 17;59(4):637-47. doi: 10.1016/0092-8674(89)90009-3.
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.
SIR1是酵母沉默交配型基因座抑制所需的几个基因之一，在HMLα基因座的抑制中具有独特作用。单细胞分析表明，具有SIR1突变等位基因的细胞，包括推定的无效等位基因，以基因相同的细胞群体形式存在，其成员处于两种不同的调控状态之一。少数细胞的HMLα基因座受到抑制，而大多数细胞的HMLα基因座处于去抑制状态。这两种状态在有丝分裂过程中是稳定的，尽管在有丝分裂生长过程中观察到状态的罕见变化，这可能反映了复制时或之前HMLα基因座的可遗传变化。对状态变化的分析表明，SIR1蛋白在沉默交配型基因抑制的建立而非维持中起作用，而SIR2、SIR3和SIR4是维持所必需的。
