Human Orc2 localizes to centrosomes, centromeres and heterochromatin during chromosome inheritance
Human Orc2 localizes to centrosomes, centromeres and heterochromatin during chromosome inheritance
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DOI：
10.1038/sj.emboj.7600255
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发表时间：
2004-07-07
期刊：
影响因子：
11.4
通讯作者：
Stillman, B
中科院分区：
文献类型：
--
作者：
Prasanth, SG;Prasanth, KV;Stillman, B
S期DNA复制的启动需要在细胞分裂周期的G1期预先组装依赖于起源识别复合体的预复制复合体在染色质上。在人类细胞中，Orc2亚单位如预期的那样定位于细胞核，但它也定位于整个细胞周期的中心体。此外，Orc2在G1期和S早期与异染色质和异染色质蛋白1α(HP1α)和HP1β紧密结合，而在S晚期、G2和M期，染色质紧密结合仅限于着丝粒。通过siRNA耗尽Orc2导致了多种表型。一组细胞显示S期缺陷，染色质上几乎没有增殖细胞核抗原，但仍有MCM蛋白存在。Orc2缺失也破坏了HP1的定位，但不影响显著异染色灶的组蛋白-H3-赖氨酸-9甲基化。另一组Orc2缺失的细胞含有复制的DNA，染色体异常浓缩，染色体聚集失败，并有多个中心体。这些结果表明Orc2蛋白参与了染色体复制、染色体结构和中心体拷贝数控制，表明它协调染色体遗传周期的所有阶段。
The initiation of DNA replication in S phase requires the prior assembly of an origin recognition complex (ORC)-dependent pre-replicative complex on chromatin during G1 phase of the cell division cycle. In human cells, the Orc2 subunit localized to the nucleus as expected, but it also localized to centrosomes throughout the entire cell cycle. Furthermore, Orc2 was tightly bound to heterochromatin and heterochromatin protein 1alpha (HP1alpha) and HP1beta in G1 and early S phase, but during late S, G2 and M phases tight chromatin association was restricted to centromeres. Depletion of Orc2 by siRNA caused multiple phenotypes. A population of cells showed an S-phase defect with little proliferating cell nuclear antigen (PCNA) on chromatin, although MCM proteins remained. Orc2 depletion also disrupted HP1 localization, but not histone-H3-lysine-9 methylation at prominent heterochromatic foci. Another subset of Orc2-depleted cells containing replicated DNA arrested with abnormally condensed chromosomes, failed chromosome congression and multiple centrosomes. These results implicate Orc2 protein in chromosome duplication, chromosome structure and centrosome copy number control, suggesting that it coordinates all stages of the chromosome inheritance cycle.