Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Cell. 2017 Jan 12;168(1-2):121-134.e12. doi: 10.1016/j.cell.2016.12.031.
C2c2, the effector of type VI CRISPR-Cas systems, has two RNase activities-one for cutting its RNA target and the other for processing the CRISPR RNA (crRNA). Here, we report the structures of Leptotrichia shahii C2c2 in its crRNA-free and crRNA-bound states. While C2c2 has a bilobed structure reminiscent of all other Class 2 effectors, it also exhibits different structural characteristics. It contains the REC lobe with a Helical-1 domain and the NUC lobe with two HEPN domains. The two RNase catalytic pockets responsible for cleaving pre-crRNA and target RNA are independently located on Helical-1 and HEPN domains, respectively. crRNA binding induces significant conformational changes that are likely to stabilize crRNA binding and facilitate target RNA recognition. These structures provide important insights into the molecular mechanism of dual RNase activities of C2c2 and establish a framework for its future engineering as a RNA editing tool.
C2c2 是 VI 型 CRISPR-Cas 系统的效应蛋白，具有两种 RNase 活性——一种用于切割其 RNA 靶标，另一种用于加工 CRISPR RNA（crRNA）。在这里，我们报告了 Leptotrichia shahii C2c2 在无 crRNA 和结合 crRNA 状态下的结构。虽然 C2c2 具有类似于所有其他 2 类效应物的双叶结构，但它也表现出不同的结构特征。它包含具有螺旋-1 结构域的 REC 叶和具有两个 HEPN 结构域的 NUC 叶。负责切割 pre-crRNA 和靶 RNA 的两个 RNase 催化口袋分别位于螺旋-1 和 HEPN 结构域上。crRNA 结合诱导了显著的构象变化，这可能稳定 crRNA 的结合并促进靶 RNA 的识别。这些结构为 C2c2 的双 RNase 活性的分子机制提供了重要的见解，并为其作为 RNA 编辑工具的未来工程奠定了框架。
