The ability of a cell to dynamically switch its chromatin between different functional states constitutes a key mechanism regulating gene expression. Histone mark "readers" display distinct binding specificity to different histone modifications and play critical roles in regulating chromatin states. Here, we show a plant-specific histone reader SHORT LIFE (SHL) capable of recognizing both H3K27me3 and H3K4me3 via its bromo-adjacent homology (BAH) and plant homeodomain (PHD) domains, respectively. Detailed biochemical and structural studies suggest a binding mechanism that is mutually exclusive for either H3K4me3 or H3K27me3. Furthermore, we show a genome-wide co-localization of SHL with H3K27me3 and H3K4me3, and that BAH-H3K27me3 and PHD-H3K4me3 interactions are important for SHL-mediated floral repression. Together, our study establishes BAH-PHD cassette as a dual histone methyl-lysine binding module that is distinct from others in recognizing both active and repressive histone marks.

中文翻译：

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植物组蛋白阅读器SHL对H3K4me3和H3K27me3的双重识别。

细胞在不同功能状态之间动态切换其染色质的能力构成了调节基因表达的关键机制。组蛋白标记“阅读器”显示出对不同组蛋白修饰的独特结合特异性，并在调节染色质状态中起关键作用。在这里，我们展示了一种植物特有的组蛋白阅读器“短寿命”（SHL），它能够分别通过其溴邻近同源性（BAH）和植物同源域（PHD）域来识别H3K27me3和H3K4me3。详细的生化和结构研究表明，H3K4me3或H3K27me3相互排斥的结合机制。此外，我们显示了SHL与H3K27me3和H3K4me3的全基因组共定位，并且BAH-H3K27me3和PHD-H3K4me3相互作用对于SHL介导的花卉抑制很重要。一起，