Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, 230026, Hefei, China.
Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
Nat Commun. 2019 Jan 16;10(1):251. doi: 10.1038/s41467-018-08273-9.
Gene regulatory mechanisms rely on a complex network of RNA processing factors to prevent untimely gene expression. In fission yeast, the highly conserved ortholog of human ERH, called Erh1, interacts with the YTH family RNA binding protein Mmi1 to form the Erh1-Mmi1 complex (EMC) implicated in gametogenic gene silencing. However, the structural basis of EMC assembly and its functions are poorly understood. Here, we present the co-crystal structure of the EMC that consists of Erh1 homodimers interacting with Mmi1 in a 2:2 stoichiometry via a conserved molecular interface. Structure-guided mutation of the Mmi1 residue, which is required for Erh1 binding, causes defects in facultative heterochromatin assembly and gene silencing while leaving Mmi1-mediated transcription termination intact. Indeed, EMC targets masked in mmi1∆ due to termination defects are revealed in mmi1. Our study delineates EMC requirements in gene silencing and identifies an ERH interface required for interaction with an RNA binding protein.
基因调控机制依赖于 RNA 加工因子的复杂网络，以防止基因表达过早发生。在裂殖酵母中，高度保守的人类 ERH 同源物称为 Erh1，与 YTH 家族 RNA 结合蛋白 Mmi1 相互作用，形成 Erh1-Mmi1 复合物（EMC），该复合物与配子基因沉默有关。然而，EMC 组装的结构基础及其功能知之甚少。在这里，我们展示了 EMC 的共晶结构，该结构由 Erh1 同源二聚体通过保守的分子界面以 2:2 的化学计量与 Mmi1 相互作用组成。通过结构引导突变 Mmi1 残基，该残基是 Erh1 结合所必需的，导致兼性异染色质组装和基因沉默缺陷，而不影响 Mmi1 介导的转录终止。事实上，由于终止缺陷而在 mmi1∆ 中被掩盖的 EMC 靶标在 mmi1. 中被揭示。我们的研究描绘了 EMC 在基因沉默中的要求，并确定了与 RNA 结合蛋白相互作用所需的 ERH 界面。
