State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 201210 Shanghai, China.
Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 200125 Shanghai, China.
J Struct Biol. 2021 Jun;213(2):107704. doi: 10.1016/j.jsb.2021.107704. Epub 2021 Feb 9.
Human RNase MRP ribonucleoprotein complex is an essential endoribonuclease involved in the processing of ribosomal RNAs, mitochondrial RNAs and certain messenger RNAs. Its RNA subunit RMRP catalyzes the cleavage of substrate RNAs, and the protein components of RNase MRP are required for activity. RMRP mutations are associated with several types of inherited developmental disorders, but the pathogenic mechanism is largely unknown. Recent structural studies shed lights on the catalytic mechanism of yeast RNase MRP and the closely related RNase P; however, the structural and catalytic mechanism of RMRP in human RNase MRP complex remains unclear. Here we report the crystal structure of the P3 domain of RMRP in complex with the RPP20 and RPP25 proteins of human RNase MRP, which shows that the P3 RNA binds to a conserved positively-charged surface of the RPP20-RPP25 heterodimer through its distal stem and internal loop regions. The disease-related mutations of RMRP are mostly located at the protein-RNA interface and are likely to weaken the binding of P3 to RPP20-RPP25. Moreover, the structure reveals a homodimeric organization of the entire RPP20-RPP25-RMRP complex, which might mediate the dimerization of human RNase MRP complex in cells. These findings provide structural clues to the assembly and pathogenesis of human RNase MRP complex and also reveal a tetrameric feature of RPP20-RPP25 evolutionarily conserved with that of the archaeal Alba proteins.
人 RNase MRP 核糖核蛋白复合物是一种必需的内切核酸酶，参与核糖体 RNA、线粒体 RNA 和某些信使 RNA 的加工。其 RNA 亚基 RMRP 催化底物 RNA 的切割，而 RNase MRP 的蛋白成分是活性所必需的。RMRP 突变与几种遗传性发育障碍有关，但发病机制在很大程度上尚不清楚。最近的结构研究揭示了酵母 RNase MRP 和密切相关的 RNase P 的催化机制；然而，人 RNase MRP 复合物中 RMRP 的结构和催化机制仍不清楚。在这里，我们报告了人 RNase MRP 中 RMRP 的 P3 结构域与 RPP20 和 RPP25 蛋白复合物的晶体结构，该结构表明 P3 RNA 通过其远端茎和内部环区结合到 RPP20-RPP25 异二聚体的保守正电荷表面上。RMRP 的相关疾病突变主要位于蛋白-RNA 界面，可能削弱 P3 与 RPP20-RPP25 的结合。此外，该结构揭示了整个 RPP20-RPP25-RMRP 复合物的同源二聚体组织，这可能介导人 RNase MRP 复合物在细胞中的二聚化。这些发现为人 RNase MRP 复合物的组装和发病机制提供了结构线索，也揭示了 RPP20-RPP25 的四聚体特征，该特征与人源 Alba 蛋白在进化上是保守的。
