Heo Kyu, Kim Bong, Kim Kyunghwan, Choi Jongkyu, Kim Hyunjung, Zhan Yuxia, Ranish Jeffrey A, An Woojin
Department of Biochemistry and Molecular Biology, University of Southern California/Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California 90033, USA.
J Biol Chem. 2007 May 25;282(21):15476-83. doi: 10.1074/jbc.M610270200. Epub 2007 Apr 1.
The histone H3 amino-terminal tails play an important role in regulating chromatin transcription. Although the mechanisms by which the H3 tail modulates transcription are not well understood, recent discoveries of specific interactions of regulatory factors with H3 tails suggest that H3 tails are a key player in the precise regulation of transcription activity. To investigate the recruitment-based action of H3 tails in chromatin transcription, we purified H3 tail-associated proteins from HeLa cells that stably express epitope-tagged H3 tails. This approach resulted in the identification of multiple histone methyltransferase activities and transcription regulatory factors that are specifically associated with expressed H3 tail domains. Point mutations of Lys-9 and Lys-27 to block cellular modifications of the tail domains completely abolished the association of specific factors, including HP1 and several repressors. Importantly, our transcription analysis revealed that the purified factors can significantly stimulate p300-mediated transcription from chromatin templates. These results implicate that the H3 tail, when accessible in relaxed chromatin, acts as a transcriptional regulator by mediating recruitment of specific sets of cofactors.
组蛋白H3氨基末端尾巴在调节染色质转录中发挥重要作用。尽管H3尾巴调节转录的机制尚未完全清楚，但最近关于调节因子与H3尾巴特异性相互作用的发现表明，H3尾巴是转录活性精确调控的关键参与者。为了研究H3尾巴在染色质转录中基于招募的作用，我们从稳定表达表位标记H3尾巴的HeLa细胞中纯化了H3尾巴相关蛋白。这种方法导致鉴定出多种组蛋白甲基转移酶活性以及与表达的H3尾巴结构域特异性相关的转录调节因子。将赖氨酸-9和赖氨酸-27进行点突变以完全阻断尾巴结构域的细胞修饰，这完全消除了包括HP1和几种阻遏物在内的特定因子的结合。重要的是，我们的转录分析表明，纯化的因子可以显著刺激p300介导的染色质模板转录。这些结果表明，当在松弛的染色质中可及的时候，H3尾巴通过介导特定辅因子的招募而作为转录调节因子发挥作用。
