title: Human 4E-T represses translation of bound mRNAs and enhances microRNA-mediated silencing.
abstract: A key player in translation initiation is eIF4E, the mRNA 5' cap-binding protein. 4E-Transporter (4E-T) is a recently characterized eIF4E-binding protein, which regulates specific mRNAs in several developmental model systems. Here, we first investigated the role of its enrichment in P-bodies and eIF4E-binding in translational regulation in mammalian cells. Identification of the conserved C-terminal sequences that target 4E-T to P-bodies was enabled by comparison of vertebrate proteins with homologues in Drosophila (Cup and CG32016) and Caenorhabditis elegans by sequence and cellular distribution. In tether function assays, 4E-T represses bound mRNA translation, in a manner independent of these localization sequences, or of endogenous P-bodies. Quantitative polymerase chain reaction and northern blot analysis verified that bound mRNA remained intact and polyadenylated. Ectopic 4E-T reduces translation globally in a manner dependent on eIF4E binding its consensus Y30X4L site. In contrast, tethered 4E-T continued to repress translation when eIF4E-binding was prevented by mutagenesis of YX4L, and modestly enhanced the decay of bound mRNA, compared with wild-type 4E-T, mediated by increased binding of CNOT1/7 deadenylase subunits. As depleting 4E-T from HeLa cells increased steady-state translation, in part due to relief of microRNA-mediated silencing, this work demonstrates the conserved yet unconventional mechanism of 4E-T silencing of particular subsets of mRNAs.
authors: Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB21QW, UK and MRC Toxicology Unit, University of Leicester, Lancaster Road, Leicester LE19HN, UK.
authors: Anastasiia
authors: A
authors: Kamenska
authors: Wei-Ting
authors: WT
authors: Lu
authors: Dorota
authors: D
authors: Kubacka
authors: Helen
authors: H
authors: Broomhead
authors: Nicola
authors: N
authors: Minshall
authors: Martin
authors: M
authors: Bushell
authors: Nancy
authors: N
authors: Standart
mesh_terms: D029721:Drosophila Proteins / Q000032:analysis / Q000737:chemistry; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D014176:Protein Biosynthesis; D034622:RNA Interference; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism; D012367:RNA, Viral / Q000378:metabolism; D012097:Repressor Proteins / Q000032:analysis / Q000737:chemistry
chemical_list: C588413:4E-T protein, Drosophila; D029721:Drosophila Proteins; C411571:EIF4ENIF1 protein, human; D039561:Eukaryotic Initiation Factor-4E; D035683:MicroRNAs; D029543:Nucleocytoplasmic Transport Proteins; D012333:RNA, Messenger; D012367:RNA, Viral; D012097:Repressor Proteins