RACK-1 regulates let-7 microRNA expression and terminal cell differentiation in Caenorhabditis elegans.
The let-7 microRNA (miRNA) regulates cell cycle exit and terminal differentiation in the C. elegans heterochronic gene pathway. Low expression of let-7 results in retarded vulva and hypodermal cell development in C. elegans and has been associated with several human cancers. Previously, the versatile scaffold protein receptor for activated C kinase 1 (RACK1) was proposed to facilitate recruitment of the miRNA-induced silencing complex (miRISC) to the polysome and to be required for miRNA function in C. elegans and humans. Here, we show that depletion of C. elegans RACK-1 by RNAi increases let-7 miRNA levels and suppresses the retarded terminal differentiation of lateral hypodermal seam cells in mutants carrying the hypomorphic let-7(n2853) allele or lacking the let-7 family miRNA genes mir-48 and mir-241. Depletion of RACK-1 also increases the levels of precursor let-7 miRNA. When Dicer is knocked down and pre-miRNA processing is inhibited, depletion of RACK-1 still leads to increased levels of pre-let-7, suggesting that RACK-1 affects a biogenesis mechanism upstream of Dicer. No changes in the activity of the let-7 promoter or the levels of primary let-7 miRNA are associated with depletion of RACK-1, suggesting that RACK-1 affects let-7 miRNA biogenesis at the post-transcriptional level. Interestingly, rack-1 knockdown also increases the levels of a few other precursor miRNAs. Our results reveal that RACK-1 controls the biogenesis of a subset of miRNAs, including let-7, and in this way plays a role in the heterochronic gene pathway during C. elegans development.
Graduate Institute of Microbiology; College of Medicine; National Taiwan University; Taipei, Taiwan.
Yu-De
YD
Chu
Graduate Institute of Microbiology; College of Medicine; National Taiwan University; Taipei, Taiwan.
Wei-Chieh
WC
Wang
Graduate Institute of Microbiology; College of Medicine; National Taiwan University; Taipei, Taiwan; Genome and Systems Biology Degree Program; College of Life Science; National Taiwan University; Taipei, Taiwan.
Shi-An A
SA
Chen
Graduate Institute of Microbiology; College of Medicine; National Taiwan University; Taipei, Taiwan.
Yen-Ting
YT
Hsu
Graduate Institute of Microbiology; College of Medicine; National Taiwan University; Taipei, Taiwan.
Meng-Wei
MW
Yeh
Department of Molecular, Cellular, and Developmental Biology; Yale University; New Haven, CT USA.
Frank J
FJ
Slack
Graduate Institute of Microbiology; College of Medicine; National Taiwan University; Taipei, Taiwan; Genome and Systems Biology Degree Program; College of Life Science; National Taiwan University; Taipei, Taiwan; Department of Molecular, Cellular, and Developmental Biology; Yale University; New Haven, CT USA.
Shih-Peng
SP
Chan
D000818:Animals; D060565:Argonaute Proteins / Q000378:metabolism; D017173:Caenorhabditis elegans / Q000166:cytology / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D034622:RNA Interference; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism
D060565:Argonaute Proteins; D029742:Caenorhabditis elegans Proteins; D035683:MicroRNAs; C556161:RACK-1 protein, C elegans; D018160:Receptors, Cytoplasmic and Nuclear; C474488:let-7 microRNA, C elegans; D043244:Ribonuclease III
Caenorhabditis elegans; RACK1; heterochronic; let-7; microRNA