Stable X chromosome inactivation involves the PRC1 Polycomb complex and requires histone MACROH2A1 and the CULLIN3/SPOP ubiquitin E3 ligase
Stable X chromosome inactivation involves the PRC1 Polycomb complex and requires histone MACROH2A1 and the CULLIN3/SPOP ubiquitin E3 ligase
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DOI：
10.1073/pnas.0408918102
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发表时间：
2005-05-24
影响因子：
11.1
通讯作者：
van Lohuizen, M
中科院分区：
文献类型：
--
作者：
Hernádez-Muñoz, I;Lund, AH;van Lohuizen, M
X失活涉及XX雌性哺乳动物两条X染色体中的一条的稳定沉默。这一过程发生在发育的早期，涉及XIST(X-Inactive-Special Transcrip)RNA包被和多梳抑制复合体(PRC)2和PRC1蛋白的招募。这种募集导致一种最初不稳定的不活跃状态，但进一步被表观遗传标记锁定，如DNA甲基化、组蛋白低乙酰化和MACROH2 A沉积。在这里，我们报告了由SPOP和CULLIN3组成的E3泛素连接酶能够泛素化多梳族蛋白BMI1和变异型组蛋白MACROH2 A。我们发现，除了MACROH2 A外，PRC1还以一种高度动态的、细胞周期调节的方式被招募到体细胞失活的X染色体上。重要的是，RNAi介导的CULLIN3或SPOP敲除导致失活X染色体(Xi)上MACROH2 A1的丢失，导致在DNA甲基化和组蛋白去乙酰化抑制剂存在的情况下Xi重新激活。同样，在这些条件下，在MacroH2A1 RNAi上也可以看到Xi的重新激活。因此，我们认为PRO复合体参与了体细胞中X染色体失活的维持。我们进一步证明，MACROH2 A1的沉积受CULLIN3/SPOP连接酶复合体的调节，并积极参与稳定的X失活，可能是通过形成额外的表观遗传沉默层。
X inactivation involves the stable silencing of one of the two X chromosomes in XX female mammals. Initiation of this process occurs during early development and involves Xist (X-inactive-specific transcript) RNA coating and the recruitment of Polycomb repressive complex (PRC) 2 and PRC1 proteins. This recruitment results in an inactive state that is initially labile but is further locked in by epigenetic marks such as DNA methylation, histone hypoacetylation, and MACROH2A deposition. Here, we report that the E3 ubiquitin ligase consisting of SPOP and CULLIN3 is able to ubiquitinate the Polycomb group protein BMI1 and the variant histone MACROH2A. We find that in addition to MACROH2A, PRC1 is recruited to the inactivated X chromosome in somatic cells in a highly dynamic, cell cycle-regulated manner. Importantly, RNAi-mediated knock-down of CULLIN3 or SPOP results in loss of MACROH2A1 from the inactivated X chromosome (Xi), leading to reactivation of the Xi in the presence of inhibitors of DNA methylation and histone deacetylation. Likewise, Xi reactivation is also seen on MacroH2A1 RNAi under these conditions. Hence, we propose that the PRO complex is involved in the maintenance of X chromosome inactivation in somatic cells. We further demonstrate that MACROH2A1 deposition is regulated by the CULLIN3/ SPOP ligase complex and is actively involved in stable X inactivation, likely through the formation of an additional layer of epigenetic silencing.