Structural basis of histone H2A-H2B recognition by the essential chaperone FACT
Structural basis of histone H2A-H2B recognition by the essential chaperone FACT
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DOI：
10.1038/nature12242
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发表时间：
2013-07-04
期刊：
影响因子：
64.8
通讯作者：
Ladurner, Andreas G.
中科院分区：
文献类型：
--
作者：
Hondele, Maria;Stuwe, Tobias;Ladurner, Andreas G.
促进染色质转录（FACT）是一种保守的组蛋白伴侣，可在DNA转录、复制和修复过程中重组核小体并确保染色质完整性（1-6）。FACT广泛功能的关键是其识别组蛋白H2 A-H2 B（参考文献2）。然而，组蛋白H2 A-H2 B如何被识别的结构基础以及它如何与FACT的其他功能整合，包括识别组蛋白H3-H4和其他核因子，尚不清楚。在这里，我们揭示了进化上保守的FACT分子伴侣结构域Spt 16 M从嗜热毛壳菌，在复杂的H2 A-H2 B异二聚体的晶体结构。一种新的“U形转弯”基序支架在Rtt 106样模块上（7-10），包含H2 B的α 1螺旋。生物化学和体内测定验证了结构，并剖析了组蛋白尾部和H3-H4对Spt 16 M结合的贡献。此外，我们报告了连接FACT与复制聚合酶的FACT异二聚化结构域的结构。我们的研究结果表明，Spt 16 M与组蛋白发生了多种相互作用，我们认为这允许该模块逐渐侵入核小体，并阻断H2 B与DNA的最强相互作用。因此，FACT将通过重组核小体组蛋白-DNA接触的前30个碱基对来增强“核小体呼吸”。我们对分子伴侣与H2 A-H2 B的接合以及所有球状FACT结构域的结构的快照使得能够对FACT的重要分子伴侣功能进行高分辨率分析，从而阐明复合物如何促进需要核小体重组的酶的活性。
Facilitates chromatin transcription (FACT) is a conserved histone chaperone that reorganizes nucleosomes and ensures chromatin integrity during DNA transcription, replication and repair(1-6). Key to the broad functions of FACT is its recognition of histones H2A-H2B (ref. 2). However, the structural basis for how histones H2A-H2B are recognized and how this integrates with the other functions of FACT, including the recognition of histones H3-H4 and other nuclear factors, is unknown. Here we reveal the crystal structure of the evolutionarily conserved FACT chaperone domain Spt16M from Chaetomium thermophilum, in complex with the H2A-H2B heterodimer. A novel 'U-turn' motif scaffolded onto a Rtt106-like module(7-10) embraces the alpha 1 helix of H2B. Biochemical and in vivo assays validate the structure and dissect the contribution of histone tails and H3-H4 towards Spt16M binding. Furthermore, we report the structure of the FACT heterodimerization domain that connects FACT to replicative polymerases. Our results show that Spt16M makes several interactions with histones, which we suggest allow the module to invade the nucleosome gradually and block the strongest interaction of H2B with DNA. FACT would thus enhance 'nucleosome breathing' by re-organizing the first 30 base pairs of nucleosomal histone-DNA contacts. Our snapshot of the engagement of the chaperone with H2A-H2B and the structures of all globular FACT domains enable the high-resolution analysis of the vital chaperoning functions of FACT, shedding light on how the complex promotes the activity of enzymes that require nucleosome reorganization.