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Title: Structural insights into Drosophila-C3PO complex assembly and 'Dynamic Side Port' model in substrate entry and release
Authors: Mo, X. 
Yang, X.
Yuan, Y.A. 
Issue Date: 2018
Publisher: Oxford University Press
Citation: Mo, X., Yang, X., Yuan, Y.A. (2018). Structural insights into Drosophila-C3PO complex assembly and 'Dynamic Side Port' model in substrate entry and release. Nucleic Acids Research 46 (16) : 8590-8604. ScholarBank@NUS Repository.
Rights: Attribution-NonCommercial 4.0 International
Abstract: In Drosophila and human, component 3 promoter of RISC (C3PO), a heteromeric complex, enhances RISC assembly and promotes RISC activity. Here, we report crystal structure of full-length Drosophila C3PO (E126Q), an inactive C3PO mutant displaying much weaker RNA binding ability, at 2.1 Å resolution. In addition, we also report the cryo-EM structures of full-length Drosophila C3PO (E126Q), C3PO (WT) and SUMO-C3PO (WT, sumo-TRAX + Translin) particles trapped at different conformations at 12, 19.7 and 12.8 Å resolutions, respectively. Crystal structure of C3PO (E126Q) displays a half-barrel architecture consisting of two Trax/Translin heterodimers, whereas cryo-EM structures of C3PO (E126Q), C3PO (WT) and SUMO-C3PO (WT) adopt a closed football-like shape with a hollow interior cavity. Remarkably, both cryo-EM structures of Drosophila C3PO (E126Q) and Drosophila SUMO-C3PO (WT) particles contain a wide side port (?25 Å × ?30 Å versus ?15 Å × ?20 Å) for RNA substrate entry and release, formed by a pair of anti-parallel packed long 1 helices of TRAX subunits. Notably, cryo-EM structure of SUMO-C3PO showed that four copies of extra densities belonging to N-terminal SUMO tag are located at the outside shell of SUMO-C3PO particle, which demonstrated that the stoichiometry of TRAX/Translin for the in vitro expressed and assembled full-length Drosophila-SUMO-C3PO particle is 4:4, suggesting Drosophila C3PO is composed by TRAX/translin at a ratio of 4:4. Remarkably, the comparison of the cryo-EM structures suggests that the C3PO side ports regulated by 1 helices of TRAX molecules are highly dynamic. Hence, we propose that C3PO particles could adopt a 'Dynamic Side Port' model to capture/digest nucleic acid duplex substrate and release the digested fragments through the dynamic side ports. © The Author(s) 2018. Published by Oxford University Press on behalf of Nucleic Acids Research.
Source Title: Nucleic Acids Research
ISSN: 0305-1048
DOI: 10.1093/nar/gky465
Rights: Attribution-NonCommercial 4.0 International
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