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Human 4E-T represses translation of bound mRNAs and enhances microRNA-mediated silencing

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 eIF...

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Detalles Bibliográficos
Autores principales: Kamenska, Anastasiia, Lu, Wei-Ting, Kubacka, Dorota, Broomhead, Helen, Minshall, Nicola, Bushell, Martin, Standart, Nancy
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2014
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3950672/
https://www.ncbi.nlm.nih.gov/pubmed/24335285
http://dx.doi.org/10.1093/nar/gkt1265
Descripción
Sumario: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 Y(30)X(4)Lϕ site. In contrast, tethered 4E-T continued to repress translation when eIF4E-binding was prevented by mutagenesis of YX(4)Lϕ, 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.