Cryo-EM Structures of Human Drosha and DGCR8 in Complex with Primary MicroRNA
Cryo-EM Structures of Human Drosha and DGCR8 in Complex with Primary MicroRNA
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DOI：
10.1016/j.molcel.2020.02.016
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发表时间：
2020-05-07
期刊：
影响因子：
16
通讯作者：
Nam, Yunsun
中科院分区：
文献类型：
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作者：
Partin, Alexander C.;Zhang, Kaiming;Nam, Yunsun
后生动物的microRNA需要由微处理器启动特定的成熟步骤，包括DROSHA和Dgcr8。缺乏组装的复合体的结构信息阻碍了对微处理器如何识别初级microRNA转录本(pri-miRNAs)的理解。在这里，我们提出了一种人类微处理器的冷冻电子显微镜结构，其中Pri-miRNA对接在活性部位，准备切割。基础连接被DROSHA中的四向分子内连接识别，该连接由夹在单链RNA上的带和楔形区触发。这条带对pri-miRNA处理的效率和准确性很重要。两个dsRBD形成了一把分子尺子，用来测量两个dsRNA-ssRNA连接之间的茎长度。DsRBD在顶端连接附近的特定组织与DROSHA核心域无关，如在部分对接状态的第二结构中观察到的那样。总的来说，我们推导了一个分子模型来解释微处理器如何识别pri-miRNA并准确地识别切割位点。
Metazoan microRNAs require specific maturation steps initiated by Microprocessor, comprising Drosha and DGCR8. Lack of structural information for the assembled complex has hindered an understanding of how Microprocessor recognizes primary microRNA transcripts (pri-miRNAs). Here we present a cryoelectron microscopy structure of human Microprocessor with a pri-miRNA docked in the active site, poised for cleavage. The basal junction is recognized by a four-way intramolecular junction in Drosha, triggered by the Belt and Wedge regions that clamp over the ssRNA. The belt is important for efficiency and accuracy of pri-miRNA processing. Two dsRBDs form a molecular ruler to measure the stem length between the two dsRNA-ssRNA junctions. The specific organization of the dsRBDs near the apical junction is independent of Drosha core domains, as observed in a second structure in the partially docked state. Collectively, we derive a molecular model to explain how Microprocessor recognizes a pri-miRNA and accurately identifies the cleavage site.