Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
Department of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
Science. 2017 Sep 15;357(6356):1142-1145. doi: 10.1126/science.aan1121. Epub 2017 Aug 17.
Gene silencing by Polycomb complexes is central to eukaryotic development. Cold-induced epigenetic repression of () in the plant provides an opportunity to study initiation and maintenance of Polycomb silencing. Here, we show that a subset of Polycomb repressive complex 2 factors nucleate silencing in a small region within , locally increasing H3K27me3 levels. This nucleation confers a silenced state that is metastably inherited, with memory held in the local chromatin. Metastable memory is then converted to stable epigenetic silencing through separate Polycomb factors, which spread across the locus after cold to enlarge the domain that contains H3K27me3. Polycomb silencing at thus has mechanistically distinct phases, which involve specialization of distinct Polycomb components to deliver first metastable then long-term epigenetic silencing.
多梳抑制复合物的基因沉默是真核生物发育的核心。植物中冷诱导的 () 的表观遗传抑制为研究多梳抑制的起始和维持提供了机会。在这里，我们表明多梳抑制复合物 2 因子的一个亚基在 内的一个小区域内引发沉默，局部增加 H3K27me3 水平。这种成核赋予沉默状态，该状态具有亚稳态遗传，局部染色质中保持记忆。然后，通过单独的多梳因子将亚稳态记忆转化为稳定的表观遗传沉默，这些因子在冷处理后扩散到整个基因座，以扩大包含 H3K27me3 的区域。因此， 处的多梳沉默具有机制上不同的阶段，涉及到不同的多梳成分的专业化，以首先传递亚稳态，然后传递长期的表观遗传沉默。
