文章基本信息

标题：Structural mechanism for the recognition and ubiquitination of a single nucleosome residue by Rad6–Bre1
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作者：Laura D. Gallego ; Medini Ghodgaonkar Steger ; Anton A. Polyansky 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：38
页码：10553-10558
DOI：10.1073/pnas.1606863113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Cotranscriptional ubiquitination of histone H2B is key to gene regulation. The yeast E3 ubiquitin ligase Bre1 (human RNF20/40) pairs with the E2 ubiquitin conjugating enzyme Rad6 to monoubiquitinate H2B at Lys123. How this single lysine residue on the nucleosome core particle (NCP) is targeted by the Rad6–Bre1 machinery is unknown. Using chemical cross-linking and mass spectrometry, we identified the functional interfaces of Rad6, Bre1, and NCPs in a defined in vitro system. The Bre1 RING domain cross-links exclusively with distinct regions of histone H2B and H2A, indicating a spatial alignment of Bre1 with the NCP acidic patch. By docking onto the NCP surface in this distinct orientation, Bre1 positions the Rad6 active site directly over H2B Lys123. The Spt–Ada–Gcn5 acetyltransferase (SAGA) H2B deubiquitinase module competes with Bre1 for binding to the NCP acidic patch, indicating regulatory control. Our study reveals a mechanism that ensures site-specific NCP ubiquitination and fine-tuning of opposing enzymatic activities.
关键词：nucleosome ; ubiquitin ; Bre1–Rad6 ; cross-linking mass spectrometry ; RING E3 ligase