Departments of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.
Proc Natl Acad Sci U S A. 2012 Nov 6;109(45):18505-10. doi: 10.1073/pnas.1202070109. Epub 2012 Oct 22.
Histone H3 lysine 4 trimethylation (H3K4me3) is a hallmark of transcription initiation, but how H3K4me3 is demethylated during gene repression is poorly understood. Jhd2, a JmjC domain protein, was recently identified as the major H3K4me3 histone demethylase (HDM) in Saccharomyces cerevisiae. Although JHD2 is required for removal of methylation upon gene repression, deletion of JHD2 does not result in increased levels of H3K4me3 in bulk histones, indicating that this HDM is unable to demethylate histones during steady-state conditions. In this study, we showed that this was due to the negative regulation of Jhd2 activity by histone H3 lysine 14 acetylation (H3K14ac), which colocalizes with H3K4me3 across the yeast genome. We demonstrated that loss of the histone H3-specific acetyltransferases (HATs) resulted in genome-wide depletion of H3K4me3, and this was not due to a transcription defect. Moreover, H3K4me3 levels were reestablished in HAT mutants following loss of JHD2, which suggested that H3-specific HATs and Jhd2 serve opposing functions in regulating H3K4me3 levels. We revealed the molecular basis for this suppression by demonstrating that H3K14ac negatively regulated Jhd2 demethylase activity on an acetylated peptide in vitro. These results revealed the existence of a general mechanism for removal of H3K4me3 following gene repression.
组蛋白 H3 赖氨酸 4 三甲基化（H3K4me3）是转录起始的标志，但在基因抑制过程中 H3K4me3 如何被去甲基化仍知之甚少。Jhd2 是一种 JmjC 结构域蛋白，最近被鉴定为酿酒酵母中主要的 H3K4me3 组蛋白去甲基酶（HDM）。尽管 JHD2 在基因抑制时去除甲基化是必需的，但 JHD2 的缺失并不会导致大量组蛋白中 H3K4me3 水平的增加，这表明这种 HDM 无法在稳态条件下去除组蛋白上的甲基。在本研究中，我们表明这是由于组蛋白 H3 赖氨酸 14 乙酰化（H3K14ac）对 Jhd2 活性的负调控所致，H3K14ac 与 H3K4me3 在整个酵母基因组中共同定位。我们证明，失去组蛋白 H3 特异性乙酰转移酶（HATs）会导致整个基因组中 H3K4me3 的耗竭，这并不是由于转录缺陷所致。此外，在 JHD2 缺失后，HAT 突变体中的 H3K4me3 水平得到了重建，这表明 H3 特异性 HATs 和 Jhd2 在调节 H3K4me3 水平方面具有相反的功能。我们通过证明 H3K14ac 在体外对乙酰化肽的 Jhd2 去甲基酶活性具有负调控作用，揭示了这种抑制的分子基础。这些结果揭示了基因抑制后去除 H3K4me3 的一般机制的存在。
