Graduate School of Natural Sciences, Nagoya City University, Nagoya, Japan.
Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
EMBO Rep. 2019 Oct 4;20(10):e48111. doi: 10.15252/embr.201948111. Epub 2019 Aug 29.
The methylation of histone H3 at lysine 9 (H3K9me), performed by the methyltransferase Clr4/SUV39H, is a key event in heterochromatin assembly. In fission yeast, Clr4, together with the ubiquitin E3 ligase Cul4, forms the Clr4 methyltransferase complex (CLRC), whose physiological targets and biological role are currently unclear. Here, we show that CLRC-dependent H3 ubiquitylation regulates Clr4's methyltransferase activity. Affinity-purified CLRC ubiquitylates histone H3, and mass spectrometric and mutation analyses reveal that H3 lysine 14 (H3K14) is the preferred target of the complex. Chromatin immunoprecipitation analysis shows that H3K14 ubiquitylation (H3K14ub) is closely associated with H3K9me-enriched chromatin. Notably, the CLRC-mediated H3 ubiquitylation promotes H3K9me by Clr4, suggesting that H3 ubiquitylation is intimately linked to the establishment and/or maintenance of H3K9me. These findings demonstrate a cross-talk mechanism between histone ubiquitylation and methylation that is involved in heterochromatin assembly.
组蛋白 H3 赖氨酸 9 位的甲基化（H3K9me）由甲基转移酶 Clr4/SUV39H 完成，是异染色质组装的关键事件。在裂殖酵母中，Clr4 与泛素 E3 连接酶 Cul4 一起形成 Clr4 甲基转移酶复合物（CLRC），其生理靶标和生物学作用目前尚不清楚。在这里，我们表明 CLRC 依赖性 H3 泛素化调节 Clr4 的甲基转移酶活性。亲和纯化的 CLRC 泛素化组蛋白 H3，质谱分析和突变分析表明 H3 赖氨酸 14（H3K14）是该复合物的首选靶标。染色质免疫沉淀分析表明 H3K14 泛素化（H3K14ub）与富含 H3K9me 的染色质密切相关。值得注意的是，CLRC 介导的 H3 泛素化通过 Clr4 促进 H3K9me，表明 H3 泛素化与 H3K9me 的建立和/或维持密切相关。这些发现表明组蛋白泛素化和甲基化之间存在一种相互作用的机制，参与异染色质的组装。
