Histone H2B deubiquitination is performed by numerous deubiquitinases in eukaryotic cells including Ubp8, the catalytic subunit of the tetrameric deubiquitination module (DUBm: Ubp8; Sus1; Sgf11; Sgf73) of the Spt-Ada-Gcn5 acetyltransferase (SAGA). Ubp8 is linked to the rest of SAGA through Sgf73 and is activated by the adaptors Sus1 and Sgf11. It is unknown if DUBm/Ubp8 might also work in a SAGA-independent manner. Here we report that a tetrameric DUBm is assembled independently of the SAGA–CORE components SPT7, ADA1 and SPT20. In the absence of SPT7, i.e., independent of the SAGA complex, Ubp8 and Sus1 are poorly recruited to SAGA-dependent genes and to chromatin. Notably, cells lacking Spt7 or Ada1, but not Spt20, show lower levels of nuclear Ubp8 than wild-type cells, suggesting a possible role for SAGA–CORE subunits in Ubp8 localization. Last, deletion of SPT7 leads to defects in Ubp8 deubiquitinase activity in in vivo and in vitro assays. Collectively, our studies show that the DUBm tetrameric structure can form without a complete intact SAGA–CORE complex and that it includes full-length Sgf73. However, subunits of this SAGA–CORE influence DUBm association with chromatin, its localization and its activity.

中文翻译：

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SAGA–CORE亚基Spt7是正确的Ubp8定位，染色质缔合和去泛素酶活性所必需的

组蛋白H2B去泛素化作用是由真核细胞中的许多去泛素化酶完成的，包括Ubp8，Ubp8是Spt-Ada-Gcn5乙酰转移酶（SAGA）的四聚体去泛素化模块的催化亚基（DUBm：Ubp8; Sus1; Sgf11; Sgf73）。Ubp8通过Sgf73链接到SAGA的其余部分，并由适配器Sus1和Sgf11激活。尚不清楚DUBm / Ubp8是否也可以以SAGA独立的方式工作。在这里，我们报告说，四聚体DUBm的组装独立于SAGA-CORE组件SPT7，ADA1和SPT20。在不存在SPT7（即独立于SAGA复合物）的情况下，Ubp8和Sus1很难募集至SAGA依赖性基因和染色质。值得注意的是，缺少Spt7或Ada1而不是Spt20的细胞显示出比野生型细胞更低的核Ubp8水平，这表明SAGA-CORE亚基在Ubp8定位中可能发挥作用。持续，在体内和体外测定中，SPT7的缺失导致Ubp8去泛素酶活性的缺陷。总的来说，我们的研究表明DUBm四聚体结构可以在没有完整的完整SAGA-CORE复合物的情况下形成，并且它包含全长Sgf73。但是，此SAGA-CORE的亚基会影响DUBm与染色质的结合，其定位及其活性。