title: A novel function for the DEAD-box RNA helicase DDX-23 in primary microRNA processing in Caenorhabditis elegans.
abstract: Primary microRNAs (pri-miRNAs) are cleaved by the nuclear RNase III Drosha to produce hairpin-shaped precursor miRNAs (pre-miRNAs). In humans, this process is known to be facilitated by the DEAD-box helicases p68 (DDX5) and p72 (DDX17). In this study, we performed a candidate-based RNAi screen in C. elegans to identify DEAD/H-box proteins involved in miRNA biogenesis. In a let-7(mg279) sensitized genetic background, knockdown of a homolog of yeast splicing factor Prp28p, DDX-23, or a homolog of human helicases p68 and p72, DDX-17, enhanced let-7 loss-of-function phenotypes, suggesting that these helicases play a role in let-7 processing and/or function. In both ddx-23(RNAi) and ddx-17(RNAi), levels of mature let-7 were decreased while pri-let-7 was found to accumulate, indicating that the helicases likely act at the level of pri-let-7 processing. DDX-23 and DDX-17 were also required for the biogenesis of other known heterochronic miRNAs, including lin-4 and the let-7 family members miR-48, miR-84 and miR-241. Their function was not confined to the heterochronic pathway, however, since they were both necessary for down-regulation of cog-1 by the spatial patterning miRNA, lsy-6. Here, we present a novel function for C. elegans DDX-23 in pri-miRNA processing, and also suggest a conserved role for DDX-17 in this process.
authors.affiliation: Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.
authors.forename: Yu-De
authors.initials: YD
authors.lastname: Chu
authors.affiliation: Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.
authors.forename: Hsin-Kai
authors.initials: HK
authors.lastname: Chen
authors.affiliation: Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.
authors.forename: Tao
authors.initials: T
authors.lastname: Huang
authors.affiliation: Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan; Genome and Systems Biology Degree Program, College of Life Science, National Taiwan University, Taipei 10617, Taiwan. Electronic address: shihpengchan@ntu.edu.tw.
authors.forename: Shih-Peng
authors.initials: SP
authors.lastname: Chan
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000201:enzymology* / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007814:Larva / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D034622:RNA Interference; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*
chemical_list: D029742:Caenorhabditis elegans Proteins; D035683:MicroRNAs; C474488:let-7 microRNA, C elegans; D049452:Green Fluorescent Proteins; C534361:DDX-23 protein, C elegans; D053487:DEAD-box RNA Helicases
keywords: C. elegans; DDX-17; DDX-23; DEAD-box RNA helicase; let-7; microRNA biogenesis