Uchimura Yasuhiro, Ichimura Takaya, Uwada Junsuke, Tachibana Taro, Sugahara Satoko, Nakao Mitsuyoshi, Saitoh Hisato
Department of Regeneration Medicine, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 860-0811, Japan.
J Biol Chem. 2006 Aug 11;281(32):23180-90. doi: 10.1074/jbc.M602280200. Epub 2006 Jun 5.
Small ubiquitin-related modifiers, SUMO-2/3 and SUMO-1, are involved in gene regulation and nuclear structures. However, little is known about the roles of SUMO, in heterochromatin formation of mammalian cells. Here we demonstrate that SUMOs directly interact with human MCAF1, which forms complexes with either the methyl-CpG-binding protein MBD1 or SETDB1, which trimethylates histone H3 at lysine 9 (H3-K9) in the presence of MCAF1. Modification of MBD1 with either SUMO-2/3 or SUMO-1 facilitated the interaction between MBD1 and MCAF1, suggesting that SUMOylation links the methylation of DNA and histones. In a cultured human cell line, SUMOs were localized in MBD1- and MCAF1-containing heterochromatin regions that were enriched in trimethyl-H3-K9 and the heterochromatin proteins HP1beta and HP1gamma. Specific knockdown of either SUMO-2/3 or SUMO-1 induced dissociation of MCAF1, trimethyl-H3-K9, and the HP1 proteins from the MBD1-containing heterochromatin foci, suggesting a requirement for SUMOs for heterochromatin assembly. These findings provide insights into the roles of SUMOylation in the regulation of heterochromatin formation and gene silencing.
小泛素相关修饰物SUMO-2/3和SUMO-1参与基因调控和核结构。然而，关于SUMO在哺乳动物细胞异染色质形成中的作用知之甚少。在此，我们证明SUMO直接与人MCAF1相互作用，MCAF1与甲基化CpG结合蛋白MBD1或SETDB1形成复合物，在MCAF1存在的情况下，SETDB1使组蛋白H3赖氨酸9（H3-K9）发生三甲基化。用SUMO-2/3或SUMO-1修饰MBD1促进了MBD1与MCAF1之间的相互作用，表明SUMO化连接了DNA和组蛋白的甲基化。在一种培养的人类细胞系中，SUMO定位于含有MBD1和MCAF1的异染色质区域，这些区域富含三甲基化H3-K9以及异染色质蛋白HP1β和HP1γ。特异性敲低SUMO-2/3或SUMO-1会导致MCAF1、三甲基化H3-K9和HP1蛋白从含有MBD1的异染色质焦点解离，表明异染色质组装需要SUMO。这些发现为SUMO化在异染色质形成调控和基因沉默中的作用提供了见解。
