小柯机器人

韩国国立首尔大学Soung-Hun Roh等研究人员合作揭示人类DICER-pre-miRNA复合物在切割状态下的结构。2023年2月22日，《自然》杂志在线发表了这一最新研究成果。

研究人员表示，Dicer在小RNA的生物生成中起着关键作用，其加工双链RNA（dsRNA）。人类DICER（hDICER，也称为DICER1）专门用于切割小发夹结构，如前体microRNA（pre-miRNA），对长dsRNA的活性有限，这与低等真核生物和植物中的同源物不同，后者可切割长dsRNA。尽管长dsRNA被切割的机制已被很好地记录下来，但人们对pre-miRNA加工的理解是不完整的，因为缺乏催化状态下的hDICER结构。

研究人员报告了hDICER在切割状态下与pre-miRNA结合的冷冻电镜结构，并揭示了pre-miRNA加工的结构基础。螺旋酶结构域变得灵活，这使得pre-miRNA能够与催化谷结合。双链RNA结合结构域通过对新发现的“GYM模体”的序列无关性和序列特异性识别，将pre-miRNA重新定位并固定在一个特定的位置。DICER特有的PAZ螺旋也被重新定向以容纳RNA。此外，这个结构确定了pre-miRNA的5′端插入到一个基本口袋的配置。在这个口袋里，一组精氨酸残基识别5′端碱基（不倾向鸟嘌呤）和末端单磷酸；这解释了hDICER的特异性以及它如何决定切割位点。研究人员确定了损害miRNA生物生成的5′口袋残基中的癌症相关突变。这项研究揭示了hDICER如何以严格的特异性识别pre-miRNA，并使人们能够从机理上理解与hDICER有关的疾病。

附：英文原文

Title: Structure of the human DICER–pre-miRNA complex in a dicing state

Author: Lee, Young-Yoon, Lee, Hansol, Kim, Haedong, Kim, V. Narry, Roh, Soung-Hun

Issue&Volume: 2023-02-22

Abstract: Dicer has a key role in small RNA biogenesis, processing double-stranded RNAs (dsRNAs)1,2. Human DICER (hDICER, also known as DICER1) is specialized for cleaving small hairpin structures such as precursor microRNAs (pre-miRNAs) and has limited activity towards long dsRNAs—unlike its homologues in lower eukaryotes and plants, which cleave long dsRNAs. Although the mechanism by which long dsRNAs are cleaved has been well documented, our understanding of pre-miRNA processing is incomplete because structures of hDICER in a catalytic state are lacking. Here we report the cryo-electron microscopy structure of hDICER bound to pre-miRNA in a dicing state and uncover the structural basis of pre-miRNA processing. hDICER undergoes large conformational changes to attain the active state. The helicase domain becomes flexible, which allows the binding of pre-miRNA to the catalytic valley. The double-stranded RNA-binding domain relocates and anchors pre-miRNA in a specific position through both sequence-independent and sequence-specific recognition of the newly identified ‘GYM motif’3. The DICER-specific PAZ helix is also reoriented to accommodate the RNA. Furthermore, our structure identifies a configuration of the 5′ end of pre-miRNA inserted into a basic pocket. In this pocket, a group of arginine residues recognize the 5′ terminal base (disfavouring guanine) and terminal monophosphate; this explains the specificity of hDICER and how it determines the cleavage site. We identify cancer-associated mutations in the 5′ pocket residues that impair miRNA biogenesis. Our study reveals how hDICER recognizes pre-miRNAs with stringent specificity and enables a mechanistic understanding of hDICER-related diseases.

DOI: 10.1038/s41586-023-05723-3

Source: https://www.nature.com/articles/s41586-023-05723-3

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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