title: LIN-28 and the poly(U) polymerase PUP-2 regulate let-7 microRNA processing in Caenorhabditis elegans.
abstract: The let-7 microRNA (miRNA) is an ultraconserved regulator of stem cell differentiation and developmental timing and a candidate tumor suppressor. Here we show that LIN-28 and the poly(U) polymerase PUP-2 regulate let-7 processing in Caenorhabditis elegans. We demonstrate that lin-28 is necessary and sufficient to block let-7 activity in vivo; LIN-28 directly binds let-7 pre-miRNA to prevent Dicer processing. Moreover, we have identified a poly(U) polymerase, PUP-2, which regulates the stability of LIN-28-blockaded let-7 pre-miRNA and contributes to LIN-28-dependent regulation of let-7 during development. We show that PUP-2 and LIN-28 interact directly, and that LIN-28 stimulates uridylation of let-7 pre-miRNA by PUP-2 in vitro. Our results demonstrate that LIN-28 and let-7 form an ancient regulatory switch, conserved from nematodes to humans, and provide insight into the mechanism of LIN-28 action in vivo. Uridylation by a PUP-2 ortholog might regulate let-7 and additional miRNAs in other species. Given the roles of Lin28 and let-7 in stem cell and cancer biology, we propose that such poly(U) polymerases are potential therapeutic targets.
authors.affiliation: Wellcome Trust Cancer Research UK Gurdon Institute, University of Cambridge, The Henry Wellcome Building of Cancer and Developmental Biology, Cambridge, UK.
authors.forename: Nicolas J
authors.initials: NJ
authors.lastname: Lehrbach
authors.forename: Javier
authors.initials: J
authors.lastname: Armisen
authors.forename: Helen L
authors.initials: HL
authors.lastname: Lightfoot
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Murfitt
authors.forename: Anthony
authors.initials: A
authors.lastname: Bugaut
authors.forename: Shankar
authors.initials: S
authors.lastname: Balasubramanian
authors.forename: Eric A
authors.initials: EA
authors.lastname: Miska
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000502:physiology*; D002454:Cell Differentiation; D005786:Gene Expression Regulation; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000378:metabolism / Q000502:physiology*; D012323:RNA Processing, Post-Transcriptional; D012097:Repressor Proteins / Q000235:genetics* / Q000502:physiology*; D043244:Ribonuclease III / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid
chemical_list: D029742:Caenorhabditis elegans Proteins; C452195:LIN-28 protein, C elegans; D035683:MicroRNAs; D012097:Repressor Proteins; C474488:let-7 microRNA, C elegans; D009713:Nucleotidyltransferases; C022428:poly U polymerase; D043244:Ribonuclease III