MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, UK.
Department of Biochemistry, University of Cambridge, Cambridge, UK.
EMBO J. 2018 Oct 1;37(19). doi: 10.15252/embj.201899021. Epub 2018 Aug 13.
The eukaryotic replisome disassembles parental chromatin at DNA replication forks, but then plays a poorly understood role in the re-deposition of the displaced histone complexes onto nascent DNA. Here, we show that yeast DNA polymerase α contains a histone-binding motif that is conserved in human Pol α and is specific for histones H2A and H2B. Mutation of this motif in budding yeast cells does not affect DNA synthesis, but instead abrogates gene silencing at telomeres and mating-type loci. Similar phenotypes are produced not only by mutations that displace Pol α from the replisome, but also by mutation of the previously identified histone-binding motif in the CMG helicase subunit Mcm2, the human orthologue of which was shown to bind to histones H3 and H4. We show that chromatin-derived histone complexes can be bound simultaneously by Mcm2, Pol α and the histone chaperone FACT that is also a replisome component. These findings indicate that replisome assembly unites multiple histone-binding activities, which jointly process parental histones to help preserve silent chromatin during the process of chromosome duplication.
真核复制体在 DNA 复制叉处使亲本染色质解聚，但随后在将置换的组蛋白复合物重新沉积到新生 DNA 上的过程中发挥了作用，其作用尚不清楚。在这里，我们表明酵母 DNA 聚合酶 α 含有一个组蛋白结合基序，该基序在人类 Pol α 中保守，并且特异性结合组蛋白 H2A 和 H2B。在芽殖酵母细胞中突变该基序不会影响 DNA 合成，但会破坏端粒和交配型基因座的基因沉默。不仅由将 Pol α 从复制体上置换的突变产生的类似表型，而且由先前在 CMG 解旋酶亚基 Mcm2 中鉴定的组蛋白结合基序的突变产生类似表型，其人类同源物被证明与组蛋白 H3 和 H4 结合。我们表明，染色质衍生的组蛋白复合物可以同时被 Mcm2、Pol α 和组蛋白伴侣 FACT 结合，FACT 也是复制体的组成部分。这些发现表明，复制体组装将多种组蛋白结合活性结合在一起，这些活性共同处理亲本组蛋白，有助于在染色体复制过程中保存沉默染色质。
