Cooperation at a distance between silencers and proto-silencers at the yeast HML locus
Cooperation at a distance between silencers and proto-silencers at the yeast HML locus
复制标题
DOI：
10.1002/j.1460-2075.1996.tb00572.x
复制
发表时间：
1996-05-01
期刊：
影响因子：
11.4
通讯作者：
Gilson, E
中科院分区：
文献类型：
--
作者：
Boscheron, C;Maillet, L;Gilson, E
沉默酵母交配型基因座的转录抑制是通过在称为沉默子的特定顺式作用元件处形成特定的核蛋白复合物来实现的。这种复合物反过来似乎启动组蛋白结合蛋白复合物扩散到周围的染色质中，这限制了该区域对转录机制的可接近性。我们通过研究整合在HML基因座处的报告基因的阻遏，研究了沉默子之间的长距离合作效应，所述HML基因座两侧是野生型和突变沉默子序列的各种组合，两个沉默子可以在超过4000 bp的范围内合作以有效地抑制转录。更重要的是，阻遏物激活蛋白1（Rap 1）、自主复制序列（ARS）结合因子1（Abf 1）或起源识别复合物（ORC）的单一结合位点可以增强远端沉默物的作用，而不会单独充当沉默物。功能协同性使用阻遏的定量测定来证明，并且随着所使用的结合位点的亲和力而变化。由于阻遏机制是Sir依赖性的，所以与远距离的I）NB元件结合的Rap 1、ORC和/或Abf 1蛋白可以相互作用以产生足够高亲和力的界面，使得含Sir的复合物结合，使沉默的染色质状态成核。
Transcriptional repression at the silent yeast mating type loci is achieved through the formation of a particular nucleoprotein complex at specific cis-acting elements called silencers. This complex in turn appears to initiate the spreading of a histone binding protein complex into the surrounding chromatin, which restricts accessibility of the region to the transcription machinery, We have investigated long-range, cooperative effects between silencers by studying the repression of a reporter gene integrated at the HML locus flanked by various combinations of wild-type and mutated silencer sequences, Two silencers can cooperate over >4000 bp to repress transcription efficiently. More importantly, a single binding site for either the repressor activator protein 1 (Rap1), the autonomous replicating sequence (ARS) binding factor 1 (Abf1) or the origin recognition complex (ORC) can enhance the action of a distant silencer without acting as a silencer on its own. Functional cooperativity is demonstrated using a quantitative assay for repression, and varies with the affinity of the binding sites used, Since the repression mechanism is Sir dependent, the Rap1, ORC and/or Abf1 proteins bound to distant I)NB elements may interact to create an interface of sufficiently high affinity such that Sir-containing complexes bind, nucleating the silent chromatin state.