PDF(Pubmed)
Abstract：
Histone H3 lysine-9 methylation (H3K9me) is a hallmark of the condensed and transcriptionally silent heterochromatin. It remains unclear how H3K9me controls transcription silencing and how cells delimit H3K9me domains to avoid silencing essential genes. Here, using Arabidopsis genetic systems that induce H3K9me2 in genes and transposons de novo, we show that H3K9me2 accumulation paradoxically also causes the deposition of the euchromatic mark H3K36me3 by a SET domain methyltransferase, ASHH3. ASHH3-induced H3K36me3 confers anti-silencing by preventing the demethylation of H3K4me1 by LDL2, which mediates transcriptional silencing downstream of H3K9me2. These results demonstrate that H3K9me2 not only facilitates but orchestrates silencing by actuating antagonistic silencing and anti-silencing pathways, providing insights into the molecular basis underlying proper partitioning of chromatin domains and the creation of metastable epigenetic variation.
摘要：
组蛋白H3赖氨酸-9甲基化（H3K9me）是凝聚和转录沉默的异染色质的标志。目前尚不清楚H3K9me如何控制转录沉默以及细胞如何界定H3K9me结构域以避免沉默必需基因。这里,利用拟南芥遗传系统在基因和转座子中从头诱导H3K9me2，我们表明，H3K9me2的积累矛盾地也导致了SET结构域甲基转移酶的常色差标记H3K36me3的沉积，ASHH3.ASHH3诱导的H3K36me3通过防止LDL2对H3K4me1的去甲基化而赋予抗沉默，LDL2介导H3K9me2下游的转录沉默。这些结果表明，H3K9me2不仅促进但通过启动拮抗沉默和抗沉默途径协调沉默，提供对染色质结构域正确划分和亚稳态表观遗传变异产生的分子基础的见解。
