title: Murine cytomegalovirus encodes a miR-27 inhibitor disguised as a target.
abstract: Individual microRNAs (miRNAs) are rapidly down-regulated during conditions of cellular activation and infection, but factors mediating miRNA turnover are poorly understood. Infection of mouse cells with murine cytomegalovirus (MCMV) induces the rapid down-regulation of an antiviral cellular miRNA, miR-27. Here, we identify a transcript produced by MCMV that binds to miR-27 and mediates its degradation. UV-crosslinking and high-throughput sequencing [CRAC (UV-crosslinking and analysis of cDNA)] identified MCMV RNA segments associated with the miRNA-binding protein Argonaute 2 (Ago2). A cluster of hits mapped to a predicted miR-27-binding site in the 3'UTR of the previously uncharacterized ORF, m169. The expression kinetics of the m169 transcript correlated with degradation of miR-27 during infection, and m169 expression inhibited miR-27 functional activity in a reporter assay. siRNA knockdown of m169 demonstrated its requirement for miR-27 degradation following infection and did not affect other host miRNAs. Substitution of the miR-27-binding site in m169 to create complementarity to a different cellular miRNA, miR-24, resulted in down-regulation of only miR-24 following infection. The m169 transcript is cytoplasmic, capped, polyadenylated, and interacts with miRNA-27 through seed pairing: characteristic features of the normal messenger RNA (mRNA) targets of miRNAs. This virus-host interaction reveals a mode of miRNA regulation in which a mRNA directs the degradation of a miRNA. We speculate that RNA-mediated miRNA degradation could be a more general viral strategy for manipulating host cells.
authors.affiliation: Centre for Immunity, Infection and Evolution,  University of Edinburgh, Edinburgh EH9 3JT,  United Kingdom.
authors.forename: Valentina
authors.initials: V
authors.lastname: Libri
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Helwak
authors.forename: Pascal
authors.initials: P
authors.lastname: Miesen
authors.forename: Diwakar
authors.initials: D
authors.lastname: Santhakumar
authors.forename: Jessica G
authors.initials: JG
authors.lastname: Borger
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Kudla
authors.forename: Finn
authors.initials: F
authors.lastname: Grey
authors.forename: David
authors.initials: D
authors.lastname: Tollervey
authors.forename: Amy H
authors.initials: AH
authors.lastname: Buck
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D060565:Argonaute Proteins / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D003432:Cross-Linking Reagents / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D005786:Gene Expression Regulation / Q000528:radiation effects; D057166:High-Throughput Screening Assays; D051379:Mice; D035683:MicroRNAs / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D018146:Muromegalovirus / Q000235:genetics* / Q000528:radiation effects; D041681:NIH 3T3 Cells; D009711:Nucleotides / Q000235:genetics; D020871:RNA Stability / Q000235:genetics / Q000528:radiation effects; D034443:RNA Transport / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000235:genetics; D059467:Transcriptome / Q000235:genetics; D014466:Ultraviolet Rays
chemical_list: D020413:3' Untranslated Regions; C526735:Ago2 protein, mouse; D060565:Argonaute Proteins; D003432:Cross-Linking Reagents; D018076:DNA, Complementary; D035683:MicroRNAs; C540674:Mirn27 microRNA, mouse; D009711:Nucleotides; D012333:RNA, Messenger; D012367:RNA, Viral