AF9 Links Histone Acetylation to DOT1L-Mediated H3K79 Methylation. Homo sapiens

The recognition of modified histones by “reader” proteins constitutes a key mechanism regulating gene expression in the chromatin context. Compared with the great variety of readers for histone methylation, few protein modules that recognize histone acetylation are known. Here we show that the evolutionarily conserved YEATS domains constitute a novel family of acetyllysine readers. The human AF9 YEATS domain binds strongly to histone H3K9 acetylation and, to a lesser extent, H3K27 and H3K18 acetylation. Crystal structural studies revealed that AF9 YEATS adopts an eight-stranded immunoglobin fold and utilizes a serine-lined aromatic “sandwiching” cage for acetyllysine readout, representing a novel recognition mechanism that is distinct from that of known acetyllysine readers. Histone acetylation recognition by AF9 is important for the chromatin recruitment of the H3K79 methyltransferase DOT1L. Together, our studies identify the YEATS domain as a novel acetyllysine-binding module, thereby establishing the first direct link between histone acetylation and DOTL1-mediated H3K79 methylation in transcription control. Overall design: ChIP-seq analysis of AF9, H3K79me3, H3K9ac in Hela cells and H3K79me3 in Hela AF9 knockdown and Hela Dot1L knockdown cells.

“阅读器”蛋白识别修饰型组蛋白，是染色质环境中调控基因表达的关键机制。相较于组蛋白甲基化（histone methylation）阅读器品类丰富，目前已知的识别组蛋白乙酰化（histone acetylation）的蛋白质模块却屈指可数。本研究证实，进化上保守的YEATS结构域（YEATS domain）构成了一类全新的乙酰赖氨酸（acetyllysine）阅读器家族。人类AF9蛋白的YEATS结构域可强力结合组蛋白H3K9乙酰化修饰，对H3K27与H3K18乙酰化的结合能力相对较弱。晶体结构研究显示，AF9 YEATS结构域采用八链免疫球蛋白折叠模式，并借助由丝氨酸排布形成的芳香族“夹笼”结构实现乙酰赖氨酸识别，这代表了一种区别于已知乙酰赖氨酸阅读器的全新识别机制。AF9对组蛋白乙酰化的识别，对于H3K79甲基转移酶DOT1L的染色质招募具有重要意义。综上，本研究确认YEATS结构域为一类新型乙酰赖氨酸结合模块，首次建立了组蛋白乙酰化与DOT1L介导的H3K79甲基化在转录调控中的直接关联。整体实验设计：在Hela细胞中对AF9、H3K79me3、H3K9ac开展染色质免疫共沉淀测序（ChIP-seq）分析；同时在AF9敲低及DOT1L敲低的Hela细胞中进行H3K79me3的ChIP-seq分析。