title: MicroRNA-mediated mRNA translation activation in quiescent cells and oocytes involves recruitment of a nuclear microRNP.
abstract: MicroRNAs can promote translation of specific mRNAs in quiescent (G0) mammalian cells and immature Xenopus laevis oocytes. We report that microRNA-mediated upregulation of target mRNAs in oocytes is dependent on nuclear entry of the microRNA; cytoplasmically-injected microRNA repress target mRNAs. Components of the activation microRNP, AGO, FXR1 (FXR1-iso-a) and miR16 are present in the nucleus and cytoplasm. Importantly, microRNA target mRNAs for upregulation, Myt1, TNFα and a reporter bearing the TNFα AU-rich, microRNA target sequence, are associated with AGO in immature oocyte nuclei and AGO2 in G0 human nuclei, respectively. mRNAs that are repressed or lack target sites are not associated with nuclear AGO. Crosslinking-coupled immunopurification revealed greater association of AGO2 with FXR1 in the nucleus compared to cytoplasm. Consistently, overexpression of FXR1-iso-a rescues activation of cytoplasmically-injected RNAs and in low density, proliferating cells. These data indicate the importance of a compartmentalized AGO2-FXR1-iso-a complex for selective recruitment for microRNA-mediated upregulation.
authors.affiliation: Center for Cancer Research, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: S S
authors.initials: SS
authors.lastname: Truesdell
authors.forename: R D
authors.initials: RD
authors.lastname: Mortensen
authors.forename: M
authors.initials: M
authors.lastname: Seo
authors.forename: J C
authors.initials: JC
authors.lastname: Schroeder
authors.forename: J H
authors.initials: JH
authors.lastname: Lee
authors.forename: O
authors.initials: O
authors.lastname: LeTonqueze
authors.forename: S
authors.initials: S
authors.lastname: Vasudevan
mesh_terms: D000818:Animals; D060565:Argonaute Proteins / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D016192:Resting Phase, Cell Cycle; D015854:Up-Regulation; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000254:growth & development / Q000378:metabolism
chemical_list: D060565:Argonaute Proteins; C096916:FXR1 protein, human; D035683:MicroRNAs; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D029867:Xenopus Proteins; C095970:MYT1 kinase, Xenopus; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases