title: The C terminus of initiation factor 4E-binding protein 1 contains multiple regulatory features that influence its function and phosphorylation.
abstract: Eukaryotic initiation factor 4E (eIF4E) binds the mRNA cap structure and forms eIF4F complexes that recruit 40S subunits to the mRNA. Formation of eIF4F is blocked by eIF4E-binding proteins such as 4E-BP1, which interacts with eIF4E via a motif in the center of its 118-residue sequence. 4E-BP1 plays key roles in cell proliferation, growth, and survival. Binding of 4E-BP1 to eIF4E is regulated by hierarchical multisite phosphorylation. Here we demonstrate that three different features in the C terminus of 4E-BP1 play distinct roles in regulating its phosphorylation and function. Firstly, we identify a new phosphorylation site in its C terminus (S101). A serine or glutamate at this position is required for efficient phosphorylation at Ser65. A second C-terminal site, S112, directly affects binding of 4E-BP1 to eIF4E without influencing phosphorylation of other sites. Thirdly, a conserved C-terminal motif influences phosphorylation of multiple residues, including rapamycin-insensitive sites. These relatively long-range effects are surprising given the reportedly unstructured nature of 4E-BP1 and may imply that phosphorylation of 4E-BP1 and/or binding to eIF4E induces a more-ordered structure. 4E-BP2 and -3 lack phosphorylatable residues corresponding to both S101 and S112. However, in 4E-BP3, replacement of the alanine at the position corresponding to S112 by serine or glutamate did not confer the ability to be released from eIF4E in response to insulin.
authors.affiliation: Division of Molecular Physiology, Faculty of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom.
authors.forename: Xuemin
authors.initials: X
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Josep-Lluis
authors.initials: JL
authors.lastname: Parra
authors.forename: Anne
authors.initials: A
authors.lastname: Beugnet
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Proud
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D018797:Cell Cycle Proteins; D002455:Cell Division; D002460:Cell Line; D002470:Cell Survival; D004791:Enzyme Inhibitors / Q000494:pharmacology; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D005822:Genetic Vectors; D018698:Glutamic Acid / Q000737:chemistry; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007328:Insulin / Q000494:pharmacology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D004791:Enzyme Inhibitors; D039561:Eukaryotic Initiation Factor-4E; D007328:Insulin; D010455:Peptides; D010750:Phosphoproteins; D020033:Protein Isoforms; D005973:Glutamine; D018698:Glutamic Acid; D012694:Serine