Yao Xiao, Tang Zhanyun, Fu Xing, Yin Jingwen, Liang Yan, Li Chonghui, Li Huayun, Tian Qing, Roeder Robert G, Wang Gang
State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology Shanghai Institutes for Biological Sciences Chinese Academy of Sciences, Shanghai, China.
Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY, USA.
EMBO J. 2015 Dec 2;34(23):2885-902. doi: 10.15252/embj.201591279. Epub 2015 Sep 1.
The Mediator complex orchestrates multiple transcription factors with the Pol II apparatus for precise transcriptional control. However, its interplay with the surrounding chromatin remains poorly understood. Here, we analyze differential histone modifications between WT and MED23(-/-) (KO) cells and identify H2B mono-ubiquitination at lysine 120 (H2Bub) as a MED23-dependent histone modification. Using tandem affinity purification and mass spectrometry, we find that MED23 associates with the RNF20/40 complex, the enzyme for H2Bub, and show that this association is critical for the recruitment of RNF20/40 to chromatin. In a cell-free system, Mediator directly and substantially increases H2Bub on recombinant chromatin through its cooperation with RNF20/40 and the PAF complex. Integrative genome-wide analyses show that MED23 depletion specifically reduces H2Bub on a subset of MED23-controlled genes. Importantly, MED23-coupled H2Bub levels are oppositely regulated during myogenesis and lung carcinogenesis. In sum, these results establish a mechanistic link between the Mediator complex and a critical chromatin modification in coordinating transcription with cell growth and differentiation.
中介体复合物协调多种转录因子与RNA聚合酶II装置，以实现精确的转录控制。然而，其与周围染色质的相互作用仍知之甚少。在这里，我们分析了野生型和MED23基因敲除（KO）细胞之间的组蛋白修饰差异，并确定赖氨酸120处的H2B单泛素化（H2Bub）是一种依赖MED23的组蛋白修饰。通过串联亲和纯化和质谱分析，我们发现MED23与H2Bub的酶RNF20/40复合物相关联，并表明这种关联对于RNF20/40募集到染色质至关重要。在无细胞系统中，中介体通过与RNF20/40和PAF复合物合作，直接并显著增加重组染色质上的H2Bub。全基因组综合分析表明，MED23缺失特异性降低了MED23控制基因子集上的H2Bub。重要的是，在肌肉生成和肺癌发生过程中，MED23偶联的H2Bub水平受到相反的调节。总之，这些结果在中介体复合物与协调转录与细胞生长和分化的关键染色质修饰之间建立了一种机制联系。
