Structural and functional studies of a noncanonical Dicer from Entamoeba histolytica.
Structural and functional studies of a noncanonical Dicer from Entamoeba histolytica.
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溶组织内阿米巴非典型切丁酶的结构和功能研究
DOI：
10.1038/srep44832
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发表时间：
2017-03-20
影响因子：
4.6
通讯作者：
Gan J
中科院分区：
文献类型：
--
作者：
Yu X;Li X;Zheng L;Ma J;Gan J
RNaseIII蛋白是dsrna特异性内切酶，参与许多重要的生物过程，如真核生物的小RNA加工和成熟。在一种原生动物寄生虫溶组织内阿米巴中发现了多种小rna。EhRNaseIII是溶组织大肠杆菌中唯一含有RNaseIII核酸内切酶结构域（RIIID）的蛋白。在这里，我们展示了三种晶体结构，揭示了EhRNaseIII的几个独特的结构特征，特别是RIIID核心结构域两侧的两个螺旋（α1和α7）之间的相互作用。结构和序列分析表明，EhRNaseIII是一个非典型Dicer，在c端区（CTR）缺乏dsRBD。体外研究表明，EhRNaseIII倾向于结合和切割较长的dsrna，产生长度约为25个核苷酸的产物。截断Aquifex aeolicus RNaseIII的CTR或连接其dsRBD可增强EhRNaseIII的结合和裂解活性。结合体外交联实验，我们的结果表明EhRNaseIII以合作模式起作用。我们推测溶组织芽胞杆菌中可能存在一些伴侣蛋白，并通过与其CTR的相互作用调节EhRNaseIII的活性。我们的研究支持EhRNaseIII在溶组织大肠杆菌产生小rna中起重要作用。
RNaseIII proteins are dsRNA-specific endonucleases involved in many important biological processes, such as small RNA processing and maturation in eukaryotes. Various small RNAs have been identified in a protozoan parasite Entamoeba histolytica. EhRNaseIII is the only RNaseIII endonuclease domain (RIIID)-containing protein in E. histolytica. Here, we present three crystal structures that reveal several unique structural features of EhRNaseIII, especially the interactions between the two helixes (α1 and α7) flanking the RIIID core domain. Structure and sequence analysis indicate that EhRNaseIII is a noncanonical Dicer and it lacks a dsRBD in the C-terminal region (CTR). In vitro studies suggest that EhRNaseIII prefers to bind and cleave longer dsRNAs, generating products around 25 nucleotides in length. Truncation of the CTR or attaching the dsRBD of Aquifex aeolicus RNaseIII can enhance the binding and cleavage activities of EhRNaseIII. In combination with in vitro crosslinking assay, our results suggested that EhRNaseIII functions in a cooperative mode. We speculate that some partner proteins may exist in E. histolytica and regulates the activity of EhRNaseIII through interaction with its CTR. Our studies support that EhRNaseIII plays an important role in producing small RNAs in E. histolytica.