Replication-coupled histone H3.1 deposition determines nucleosome composition and heterochromatin dynamics during Arabidopsis seedling development
Replication-coupled histone H3.1 deposition determines nucleosome composition and heterochromatin dynamics during Arabidopsis seedling development
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DOI：
10.1111/nph.15248
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发表时间：
2019-01-01
期刊：
影响因子：
9.4
通讯作者：
Probst, Aline V.
中科院分区：
文献类型：
--
作者：
Benoit, Matthias;Simon, Lauriane;Probst, Aline V.
发育阶段的转变通常以染色质景观的变化和异染色质重组为特征。在拟南芥中，重复的异染色位点聚集成所谓的染色质中心是核空间染色体组织的重要决定因素。在这里，我们研究了在幼苗发育早期从异养状态向光合作用状态转换过程中参与染色中心形成的分子机制。我们描述了着丝粒和着丝粒周围重复序列的空间组织和染色质特征，并鉴定了染色质中心形成受损的突变环境。我们发现，重复DNA基因座的聚集进入染色质中心发生在一个精确的时间窗口，并导致转录抑制增强。虽然重复序列在重复聚类之前富含H3K9me2和连接子组蛋白H1，但染色中心的形成涉及到异染色质的特征--H3.1和H2AW组蛋白变体的增加。这些过程在染色质组装因子1(CAF-1)介导的复制偶联组蛋白组装受损的突变体中受到严重影响。我们进一步揭示，在染色质中心形成过程中，组蛋白的沉积是H3K9me2在重复序列上高效浓缩所必需的。综上所述，我们表明，在萌发后发育过程中的染色中心组装需要核小体组成的动态变化和复制耦合H3.1沉积机制协调的组蛋白翻译后修饰。
Developmental phase transitions are often characterized by changes in the chromatin landscape and heterochromatin reorganization. In Arabidopsis, clustering of repetitive heterochromatic loci into so-called chromocenters is an important determinant of chromosome organization in nuclear space. Here, we investigated the molecular mechanisms involved in chromocenter formation during the switch from a heterotrophic to a photosynthetically competent state during early seedling development. We characterized the spatial organization and chromatin features at centromeric and pericentromeric repeats and identified mutant contexts with impaired chromocenter formation. We find that clustering of repetitive DNA loci into chromocenters takes place in a precise temporal window and results in reinforced transcriptional repression. Although repetitive sequences are enriched in H3K9me2 and linker histone H1 before repeat clustering, chromocenter formation involves increasing enrichment in H3.1 as well as H2A.W histone variants, hallmarks of heterochromatin. These processes are severely affected in mutants impaired in replication-coupled histone assembly mediated by CHROMATIN ASSEMBLY FACTOR 1 (CAF-1). We further reveal that histone deposition by CAF-1 is required for efficient H3K9me2 enrichment at repetitive sequences during chromocenter formation. Taken together, we show that chromocenter assembly during post-germination development requires dynamic changes in nucleosome composition and histone post-translational modifications orchestrated by the replication-coupled H3.1 deposition machinery.