title: Involvement of Hu and heterogeneous nuclear ribonucleoprotein K in neuronal differentiation through p21 mRNA post-transcriptional regulation.
abstract: The Hu family is a group of neuronal RNA-binding proteins required for neuronal differentiation in the developing nervous system. Previously, Hu proteins have been shown to enhance the stabilization and/or translation of target mRNAs, such as p21 (CIP1), by binding to AU-rich elements in untranslated regions (UTRs). In this study, we show that Hu induces p21 expression, cell cycle arrest, and neuronal differentiation in mouse neuroblastoma N1E-115 cells. p21 expression is also up-regulated during Me2SO-induced differentiation in N1E-115 cells and is controlled by post-transcriptional mechanisms through its 3'-UTR. To investigate the molecular mechanisms of Hu functions, we used a proteomics strategy to isolate Hu-interacting proteins and identified heterogeneous nuclear ribonucleoprotein (hnRNP) K. hnRNP K also specifically binds to CU-rich sequences in p21 mRNA 3'-UTR and represses its translation in both nonneuronal and neuronal cells. Further, using RNA interference experiments, we show that the Hu-p21 pathway contributes to the regulation of neurite outgrowth and proliferation in N1E-115 cells, and this pathway is antagonized by hnRNP K. Our results suggest a model in which the mutually antagonistic action of two RNA-binding proteins, Hu and hnRNP K, control the timing of the switch from proliferation to neuronal differentiation through the post-transcriptional regulation of p21 mRNA.
authors.affiliation: CREST-JST and the Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Yano
authors.forename: Hirotaka J
authors.initials: HJ
authors.lastname: Okano
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Okano
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001710:Biotin / Q000737:chemistry; D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21; D051959:ELAV Proteins; D017353:Gene Deletion; D005982:Glutathione Transferase / Q000378:metabolism; D034641:Heterogeneous-Nuclear Ribonucleoprotein K / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D040901:Proteomics / Q000379:methods; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D034622:RNA Interference; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D015854:Up-Regulation
chemical_list: D020413:3' Untranslated Regions; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D051959:ELAV Proteins; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012313:RNA; D001710:Biotin; D008156:Luciferases; D005982:Glutathione Transferase; D001973:Bromodeoxyuridine