Youdell Michael L, Kizer Kelby O, Kisseleva-Romanova Elena, Fuchs Stephen M, Duro Eris, Strahl Brian D, Mellor Jane
Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
Mol Cell Biol. 2008 Aug;28(16):4915-26. doi: 10.1128/MCB.00001-08. Epub 2008 Jun 9.
Set2 (KMT3)-dependent methylation (me) of histone H3 at lysine 36 (H3K36) promotes deacetylation of transcribed chromatin and represses cryptic promoters within genes. Although Set2 is the only methyltransferase (KMTase) for H3K36 in yeast, it is not known if Set2 is regulated or whether the different methylation states at H3K36 are functionally distinct. Here we show that the N-terminal 261 residues of Set2 (Set2(1-261)), containing the SET KMTase domain, are sufficient for H3K36me2, histone deacetylation, and repression of cryptic promoters at STE11. Set2-catalyzed H3K36me2 does not require either Ctk1-dependent phosphorylation of RNA polymerase II (RNAPII) or the presence of the phospho-C-terminal domain (CTD) interaction (SRI) domain of Set2. This finding is consistent with a known correlation between H3K36me2 and whether a gene is on or off, but not the level of activity of a gene. By contrast, H3K36me3 requires Spt6, proline 38 on histone H3 (H3P38), the CTD of RNAPII, Ctk1, and the C-terminal SRI domain of Set2. We suggest that the C-terminal region of Set2, in conjunction with the phosphorylated CTD of RNAPII, influences the KMTase activity to promote H3K36me3 during transcription elongation.
组蛋白H3赖氨酸36（H3K36）上的Set2（KMT3）依赖性甲基化促进转录染色质的去乙酰化，并抑制基因内的隐匿启动子。虽然Set2是酵母中H3K36唯一的甲基转移酶（KMTase），但尚不清楚Set2是否受到调控，以及H3K36的不同甲基化状态在功能上是否有差异。在这里，我们表明Set2的N端261个残基（Set2(1-261)），包含SET KMTase结构域，足以实现H3K36me2、组蛋白去乙酰化以及在STE11处抑制隐匿启动子。Set2催化的H3K36me2既不需要RNA聚合酶II（RNAPII）的Ctk1依赖性磷酸化，也不需要Set2的磷酸化C端结构域（CTD）相互作用（SRI）结构域的存在。这一发现与H3K36me2和基因是否开启之间已知的相关性一致，但与基因的活性水平无关。相比之下，H3K36me3需要Spt6、组蛋白H3上的脯氨酸38（H3P38）、RNAPII的CTD、Ctk1以及Set2的C端SRI结构域。我们认为，Set2的C端区域与RNAPII的磷酸化CTD共同作用，在转录延伸过程中影响KMTase活性以促进H3K36me3。
