title: RNA CUG-binding protein 1 increases translation of 20-kDa isoform of CCAAT/enhancer-binding protein beta by interacting with the alpha and beta subunits of eukaryotic initiation translation factor 2.
abstract: Expression of a dominant negative 20-kDa isoform of CCAAT/enhancer-binding protein (C/EBPbeta), LIP, is increased in proliferating livers and in tumor cells. Two RNA-binding proteins, CUGBP1 and calreticulin, have been implicated in the translational regulation of C/EBPbeta. In this paper, we present evidence showing several critical steps by which liver increases translation of LIP after partial hepatectomy. At early stages after partial hepatectomy, liver activates CUGBP1 by a hyperphosphorylation. The activated CUGBP1 binds to the 5' region of C/EBPbeta mRNA and replaces calreticulin, which partially represses translation of C/EBPbeta in quiescent livers. The hyperphosphorylated CUGBP1 also interacts with the alpha and beta subunits of initiation factor eIF2. Our data demonstrate that the interaction of CUGBP1 with the eIF2alpha enhances the association of CUGBP1 with ribosomes and correlates with increased translation of LIP in the liver after partial hepatectomy. Our data support the hypothesis that CUGBP1 increases translation of LIP by the interaction with the eIF2alpha subunit. This facilitates subsequent recruitment of larger numbers of ribosomes to initiate translation of LIP.
authors.affiliation: Department of Pathology and Huffington Center on Aging, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: Nikolai A
authors.initials: NA
authors.lastname: Timchenko
authors.forename: Gou-Li
authors.initials: GL
authors.lastname: Wang
authors.forename: Lubov T
authors.initials: LT
authors.lastname: Timchenko
mesh_terms: D000818:Animals; D015153:Blotting, Western; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics*; D000067879:CELF1 Protein; D037282:Calreticulin / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000235:genetics; D006367:HeLa Cells; D006498:Hepatectomy; D006801:Humans; D008099:Liver / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011993:Recombinant Fusion Proteins; D012270:Ribosomes / Q000378:metabolism; D014162:Transfection
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; D000067879:CELF1 Protein; C502743:CELF1 protein, mouse; D037282:Calreticulin; D015852:Eukaryotic Initiation Factor-2; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins