Distinct kinetic mechanisms of H3K4 methylation catalyzed by MLL3 and MLL4 core complexes.
Distinct kinetic mechanisms of H3K4 methylation catalyzed by MLL3 and MLL4 core complexes.
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MLL3和MLL4核心复合物催化H3K4甲基化的独特动力学机制
DOI：
10.1016/j.jbc.2021.100635
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发表时间：
2021-01
期刊：
影响因子：
--
通讯作者：
Quan S
中科院分区：
文献类型：
--
作者：
Zheng Y;Huang Y;Mencius J;Li Y;Zhao L;Luo W;Chen Y;Quan S
甲基转移酶MLL 3和MLL 4主要催化组蛋白H3赖氨酸4（H3 K4）在增强子上的单甲基化，以调节细胞类型特异性基因表达和细胞命运转变。MLL 3和MLL 4共享几乎相同的结合伴侣和生化活性，但执行特定的和非冗余的功能。区分MLL 3和MLL 4的特征和功能仍然难以捉摸。在这里，我们表征MLL 3和MLL 4三元复合物的动力学机制，其中包含MLL 3或MLL 4的催化SET结构域（MLL 3SET或MLL 4SET），ASH 2L的SPRY结构域（ASH 2LSPRY）和RBBP 5的短片段（RBBP 5AS-ABM），以寻找可能的解释。稳态动力学分析和抑制研究表明，MLL 3复合物催化甲基化在一个随机顺序的双-双机制。与此相反，MLL 4复合物采用有序的顺序双-双机制，其中辅因子S-腺苷甲硫氨酸（NAMet）在H3肽之前与酶结合，甲基化的H3肽在甲基化后S-腺苷高半胱氨酸（NAHcy）分离之前与酶解离。使用荧光偏振（FP）的底物结合测定证实，对于MLL 4复合物而不是MLL 3复合物，H3结合的先决条件是H3结合。分子动力学模拟表明，结合的MLL 4的H3底物结合口袋和H3底物结合沟上的H3 Met专门诱导构象约束，因此稳定的特定活性构象，以方便进入的底物H3。不同的动力学机制和构象可塑性为MLL 3和MLL 4的差异功能提供了重要的见解，也可以指导靶向MLL 3或MLL 4的选择性抑制剂的开发。
The methyltransferases MLL3 and MLL4 primarily catalyze the monomethylation of histone H3 lysine 4 (H3K4) on enhancers to regulate cell-type-specific gene expression and cell fate transition. MLL3 and MLL4 share almost identical binding partners and biochemical activities, but perform specific and nonredundant functions. The features and functions that distinguish MLL3 and MLL4 remain elusive. Here, we characterize the kinetic mechanisms of MLL3 and MLL4 ternary complexes containing the catalytic SET domain from MLL3 or MLL4 (MLL3SET or MLL4SET), the SPRY domain of ASH2L (ASH2LSPRY), and a short fragment of RBBP5 (RBBP5AS-ABM) to search for possible explanations. Steady-state kinetic analyses and inhibition studies reveal that the MLL3 complex catalyzes methylation in a random sequential bi–bi mechanism. In contrast, the MLL4 complex adopts an ordered sequential bi–bi mechanism, in which the cofactor S-adenosylmethionine (AdoMet) binds to the enzyme prior to the H3 peptide, and the methylated H3 peptide dissociates from the enzyme before S-adenosylhomocysteine (AdoHcy) detaches after methylation. Substrate-binding assays using fluorescence polarization (FP) confirm that AdoMet binding is a prerequisite for H3 binding for the MLL4 complex but not for the MLL3 complex. Molecular dynamic simulations reveal that the binding of AdoMet exclusively induces conformational constraints on the AdoMet-binding groove and the H3 substrate-binding pocket of MLL4, therefore stabilizing a specific active conformation to ease entry of the substrate H3. The distinct kinetic mechanisms and conformational plasticities provide important insights into the differential functions of MLL3 and MLL4 and may also guide the development of selective inhibitors targeting MLL3 or MLL4.
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影响因子：
16.8
作者：
Hu D;Garruss AS;Gao X;Morgan MA;Cook M;Smith ER;Shilatifard A
通讯作者：
Shilatifard A
影响因子：
5.6
作者：
Jang Y;Wang C;Zhuang L;Liu C;Ge K
通讯作者：
Ge K
影响因子：
4.4
作者：
JORGENSEN, WL;CHANDRASEKHAR, J;KLEIN, ML
通讯作者：
KLEIN, ML
影响因子：
2.9
作者：
Chin, HG;Patnaik, D;Pradhan, S
通讯作者：
Pradhan, S
影响因子：
4.4
作者：
ESSMANN, U;PERERA, L;PEDERSEN, LG
通讯作者：
PEDERSEN, LG