Program in Molecular Biophysics, Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, United States.
Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, United States.
Elife. 2019 Jan 25;8:e40988. doi: 10.7554/eLife.40988.
Monoubiquitination of histone H2B (H2B-Ub) plays a role in transcription and DNA replication, and is required for normal localization of the histone chaperone, FACT. In yeast, H2B-Ub is deubiquitinated by Ubp8, a subunit of SAGA, and Ubp10. Although they target the same substrate, loss of Ubp8 and Ubp10 cause different phenotypes and alter the transcription of different genes. We show that Ubp10 has poor activity on yeast nucleosomes, but that the addition of FACT stimulates Ubp10 activity on nucleosomes and not on other substrates. Consistent with a role for FACT in deubiquitinating H2B in vivo, a FACT mutant strain shows elevated levels of H2B-Ub. Combination of FACT mutants with deletion of Ubp10, but not Ubp8, confers increased sensitivity to hydroxyurea and activates a cryptic transcription reporter, suggesting that FACT and Ubp10 may coordinate nucleosome assembly during DNA replication and transcription. Our findings reveal unexpected interplay between H2B deubiquitination and nucleosome dynamics.
组蛋白 H2B 的单泛素化（H2B-Ub）在转录和 DNA 复制中发挥作用，并且对于组蛋白伴侣 FACT 的正常定位是必需的。在酵母中，H2B-Ub 被 SAGA 的一个亚基 Ubp8 和 Ubp10 去泛素化。尽管它们靶向相同的底物，但 Ubp8 和 Ubp10 的缺失会导致不同的表型，并改变不同基因的转录。我们表明，Ubp10 对酵母核小体的活性很差，但 FACT 的添加会刺激 Ubp10 在核小体上的活性，而不是在其他底物上。与 FACT 在体内参与 H2B 去泛素化的作用一致，FACT 突变株显示 H2B-Ub 水平升高。FACT 突变体与 Ubp10 缺失的组合，但不是 Ubp8 缺失，赋予对羟基脲的更高敏感性，并激活隐匿性转录报告基因，表明 FACT 和 Ubp10 可能在 DNA 复制和转录过程中协调核小体组装。我们的发现揭示了 H2B 去泛素化和核小体动力学之间的意外相互作用。
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