title: CBP80-promoted mRNP rearrangements during the pioneer round of translation, nonsense-mediated mRNA decay, and thereafter.
abstract: In mammalian cells, two different messenger ribonucleoproteins (mRNPs) serve as templates for protein synthesis. Newly synthesized mRNPs bound by the cap-binding protein heterodimer CBP80-CBP20 (CBC) initially undergo a pioneer round of translation. One purpose of this round of translation is to ensure the quality of gene expression, as exemplified by nonsense-mediated messenger RNA (mRNA) decay (NMD). NMD largely functions to eliminate mRNAs that prematurely terminate translation, although NMD also contributes to proper gene control, and it targets CBC-bound mRNPs. CBC-bound mRNPs are remodeled to eukaryotic translation initiation factor (eIF)4E-bound mRNPs in steps that (1) are a consequence of the pioneer round of translation and (2) occur independently of translation. Rather than supporting NMD, eIF4E-bound mRNPs provide for the bulk of cellular protein synthesis and are the primary targets of mRNA decay mechanisms that conditionally regulate gene expression. Here, we overview cellular processes by which CBC-bound mRNPs are remodeled to eIF4E-bound mRNPs. We also describe the molecular movements of certain factors during NMD in view of the influential role of CBP80.
authors: Department of Biochemistry and Biophysics, The Center for RNA Biology, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA. lynne_maquat@urmc.rochester.edu
authors: L E
authors: LE
authors: Maquat
authors: J
authors: J
authors: Hwang
authors: H
authors: H
authors: Sato
authors: Y
authors: Y
authors: Tang
mesh_terms: D000818:Animals; D018389:Codon, Nonsense / Q000235:genetics*; D006801:Humans; D039502:Nuclear Cap-Binding Protein Complex / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D014176:Protein Biosynthesis / Q000235:genetics*; D020871:RNA Stability / Q000235:genetics*; D012261:Ribonucleoproteins / Q000378:metabolism*
chemical_list: D018389:Codon, Nonsense; D039502:Nuclear Cap-Binding Protein Complex; D012261:Ribonucleoproteins; C026452:messenger ribonucleoprotein