Department of Biochemistry and Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907, USA.
J Biol Chem. 2010 Apr 9;285(15):11704-13. doi: 10.1074/jbc.M109.085043. Epub 2010 Feb 5.
Set2-mediated H3 Lys(36) methylation is a histone modification that has been demonstrated to function in transcriptional elongation by recruiting the Rpd3S histone deacetylase complex to repress intragenic cryptic transcription. Recently, we identified a trans-histone pathway in which the interaction between the N terminus of Set2 and histone H4 Lys(44) is needed to mediate trans-histone H3 Lys(36) di- and trimethylation. In the current study, we demonstrate that mutation of the lysine 44 residue in histone H4 or the Set2 mutant lacking the histone H4 interaction motif leads to intragenic cryptic transcripts, indicating that the Set2 and histone H4 interaction is important to repress intragenic cryptic transcription. We also determine that histone H2A residues (Leu(116) and Leu(117)), which are in close proximity to histone H4 Lys(44), are needed for proper trans-histone H3 Lys(36) methylation. Similar to H4 Lys(44) mutants, histone H2A Leu(116) and Leu(117) mutations exhibited decreased H3 Lys(36) di- and trimethylation, increased histone H4 acetylation, increased resistance to 6-azauracil, and cryptic transcription. Interestingly, the combined histone H4 Lys(44) and H2A mutations have more severe methylation defects and increased H4 acetylation levels. Furthermore, we identify that additional histone H2A and H3 core residues are also needed for H3 Lys(36) di- and trimethylation. Overall, our results show and suggest that multiple H4, H2A, and H3 residues contribute to and form a Set2 docking/recognition site on the nucleosomal surface so that proper Set2-mediated H3 Lys(36) di- and trimethylation, histone acetylation, and transcriptional elongation can occur.
组蛋白 H3 赖氨酸 36 位甲基化（H3 Lys(36) methylation）是一种组蛋白修饰，已被证明可通过募集 Rpd3S 组蛋白去乙酰化酶复合物来抑制基因内隐匿转录，从而在转录延伸中发挥作用。最近，我们发现了一种跨组蛋白途径，其中 Set2 的 N 端与组蛋白 H4 赖氨酸 44 位的相互作用对于介导跨组蛋白 H3 赖氨酸 36 位二甲基化和三甲基化是必需的。在本研究中，我们证明了组蛋白 H4 赖氨酸 44 位的突变或缺乏与组蛋白 H4 相互作用的 Set2 突变体导致基因内隐匿转录本的产生，这表明 Set2 和组蛋白 H4 的相互作用对于抑制基因内隐匿转录是重要的。我们还确定了组蛋白 H2A 残基（亮氨酸 116 和亮氨酸 117），它们与组蛋白 H4 赖氨酸 44 位紧密相邻，对于适当的跨组蛋白 H3 赖氨酸 36 位甲基化是必需的。与 H4 赖氨酸 44 位突变体类似，组蛋白 H2A 亮氨酸 116 和亮氨酸 117 突变体表现出 H3 赖氨酸 36 位二甲基化和三甲基化减少、组蛋白 H4 乙酰化增加、对 6-氮杂尿嘧啶的抗性增加和隐匿转录增加。有趣的是，组蛋白 H4 赖氨酸 44 位和 H2A 突变的联合具有更严重的甲基化缺陷和增加的 H4 乙酰化水平。此外，我们确定了额外的组蛋白 H2A 和 H3 核心残基也需要 H3 赖氨酸 36 位二甲基化和三甲基化。总之，我们的结果表明，多个 H4、H2A 和 H3 残基有助于并形成核小体表面上的 Set2 对接/识别位点，从而使适当的 Set2 介导的 H3 赖氨酸 36 位二甲基化和三甲基化、组蛋白乙酰化和转录延伸能够发生。
