Aparicio O M, Billington B L, Gottschling D E
Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637.
Cell. 1991 Sep 20;66(6):1279-87. doi: 10.1016/0092-8674(91)90049-5.
Genes placed near telomeres in S. cerevisiae succumb to position-effect variegation. SIR2, SIR3, SIR4, NAT1, ARD1, and HHF2 (histone H4) were identified as modifiers of the position effect at telomeres, since transcriptional repression near telomeres was no longer observed when any of the modifier genes were mutated. These genes, in addition to SIR1, have previously been shown to repress transcription at the silent mating loci, HML and HMR. However, there were differences between transcriptional silencing at telomeres and the HM loci, as demonstrated by suppressor analysis and the lack of involvement of SIR1 in telomeric silencing. These findings provide insights into telomeric structure and function that are likely to apply to many eukaryotes. In addition, the distinctions between telomeres and the HM loci suggest a hierarchy of chromosomal silencing in S. cerevisiae.
在酿酒酵母中，位于端粒附近的基因会受到位置效应斑驳的影响。SIR2、SIR3、SIR4、NAT1、ARD1和HHF2（组蛋白H4）被鉴定为端粒位置效应的修饰因子，因为当任何一个修饰基因发生突变时，端粒附近的转录抑制就不再被观察到。除了SIR1之外，这些基因先前已被证明能抑制沉默交配位点HML和HMR处的转录。然而，通过抑制子分析以及SIR1不参与端粒沉默这一现象表明，端粒处的转录沉默与HM位点之间存在差异。这些发现为端粒的结构和功能提供了见解，这些见解可能适用于许多真核生物。此外，端粒与HM位点之间的差异表明酿酒酵母中存在染色体沉默的层次结构。
