The preRC protein ORCA organizes heterochromatin by assembling histone H3 lysine 9 methyltransferases on chromatin
The preRC protein ORCA organizes heterochromatin by assembling histone H3 lysine 9 methyltransferases on chromatin
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DOI：
10.7554/elife.06496
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发表时间：
2015-04-29
期刊：
影响因子：
7.7
通讯作者：
Prasanth, Supriya G.
中科院分区：
文献类型：
--
作者：
Giri, Sumanprava;Aggarwal, Vasudha;Prasanth, Supriya G.
异色结构域富含抑制性组蛋白标记，包括由赖氨酸甲基转移酶(KMTs)写入的组蛋白H3赖氨酸9甲基化。复制前的复合体蛋白，起源识别复合体相关的(ORCA/LRWD1)，优先定位于复制后细胞的异染色区。它在异染色质组织中的作用仍然难以捉摸。Orca识别甲基化的H3K9标记，并以染色质上下文相关的方式与抑制性KMT相互作用，包括G9a/GLP和SUV39H1。单分子下拉分析表明，ORCA-ORC(Origin Recognition Complex)和多个H3K9 KMT存在于单个复合体中，ORCA稳定H3K9 KMT复合体。缺乏ORCA的细胞表现出染色质结构的变化，特定染色质部位的H3K9二甲基化和三甲基化显著减少。由于ORCA的缺失，异染色质结构的改变会影响复制时间，特别是在复制后期。我们证明ORCA是建立H3K9 KMT复合体的支架，它在特定染色质部位的结合和活性对异染色质结构的组织至关重要。
Heterochromatic domains are enriched with repressive histone marks, including histone H3 lysine 9 methylation, written by lysine methyltransferases (KMTs). The pre-replication complex protein, origin recognition complex-associated (ORCA/LRWD1), preferentially localizes to heterochromatic regions in post-replicated cells. Its role in heterochromatin organization remained elusive. ORCA recognizes methylated H3K9 marks and interacts with repressive KMTs, including G9a/GLP and Suv39H1 in a chromatin context-dependent manner. Single-molecule pull-down assays demonstrate that ORCA-ORC (Origin Recognition Complex) and multiple H3K9 KMTs exist in a single complex and that ORCA stabilizes H3K9 KMT complex. Cells lacking ORCA show alterations in chromatin architecture, with significantly reduced H3K9 di- and tri-methylation at specific chromatin sites. Changes in heterochromatin structure due to loss of ORCA affect replication timing, preferentially at the late-replicating regions. We demonstrate that ORCA acts as a scaffold for the establishment of H3K9 KMT complex and its association and activity at specific chromatin sites is crucial for the organization of heterochromatin structure.