STRUCTURAL STUDY OF THE HISTONE METHYLTRANSFERASE MLL1 COMPLEX

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 组蛋白赖氨酸甲基转移酶MLL1复合体是目前最重要的复合体之一 表观遗传学研究。该络合物的催化核心包含四个组分。MLL1、WDR5、 RbBP5和Ash2L。MLL1是催化组分。然而，MLL1本身并不具有催化活性。在其他组分存在的情况下，MLL1可以修饰组蛋白H3的赖氨酸4。 最近，我们测定了WDR5-RbBP5-Ash2L配合物的高分辨晶体结构。 它显示出一种非常灵活的构象。在晶体结构中，RbBP5与WDR5 而Ash2L和WDR5与Ash2L没有直接相互作用。来自其他实验室的数据显示 WDR5直接与MLL1结合。此外，从我们的生化研究中，我们还知道， 在WDR5-RbBP5-Ash2L亚复合体中加入MLL1可产生更高的酶活性 这种刺激需要Ash2L和RbBP5，尽管它们都不能 与MLL1自身相互作用。我们认为MLL1和WDR5之间的相互作用在 WDR5-RbBP5-Ash2L综合体招募MLL1靠近RbBP5和Ash2L 招募导致大范围的构象变化(从没有 酶活性到具有活性的更紧密的结构)，适合于检测 由SAXS提供。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Histone lysine methyltransferase MLL1 complex is one of the most important complex in current epigenetics research. The catalytic core of this complex contains four components. MLL1, WDR5, RbBP5 and Ash2L. MLL1 is the catalytic component. However, by itself, MLL1 is not catalytically active. One in the presence of the other components, MLL1 can modify lysine 4 of histone H3. Recently, we determined the high resolution crystal structure of the WDR5-RbBP5-Ash2L complex. It shows a very flexible conformation. In the crystal structure, RbBP5 contacts with both WDR5 and Ash2L and WDR5 shows no direct interaction with Ash2L. Data from other labs showed that WDR5 directly binds to MLL1. In addition, from our biochemical studies, we also know that the addition of MLL1 to the WDR5-RbBP5-Ash2L subcomplex resulted in much higher enzymatic activity than MLL1 itself and this stimulation requires Ash2L and RbBP5 although neither of them could interact with MLL1 by themselves. We propose that the interaction between MLL1 and WDR5 in the WDR5-RbBP5-Ash2L complex recruits MLL1 to close vicinity to RbBP5 and Ash2L and this recruitment results in large range conformational change (from flexible complex with no enzymatic activity to a more compact structure with activity) that is suitable for detection by SAXS.