eEF1A is a novel component of the mammalian nuclear protein export machinery.
The cytoplasmic translation factor eEF1A has been implicated in the nuclear export of tRNA species in lower eukaryotes. Here we demonstrate that eEF1A plays a central role in nuclear export of proteins in mammalian cells. TD-NEM (transcription-dependent nuclear export motif), a newly characterized nuclear export signal, mediates efficient nuclear export of several proteins including the von Hippel-Lindau (VHL) tumor suppressor and the poly(A)-binding protein (PABP1) in a manner that is dependent on ongoing RNA polymerase II (RNA PolII)-dependent transcription. eEF1A interacts specifically with TD-NEM of VHL and PABP1 and disrupting this interaction, by point mutations of key TD-NEM residues or treatment with actinomycin D, an inhibitor of RNA PolII-dependent transcription, prevents assembly and nuclear export. siRNA-induced knockdown or antibody-mediated depletion of eEF1A prevents in vivo and in vitro nuclear export of TD-NEM-containing proteins. Nuclear retention experiments and inhibition of the Exportin-5 pathway suggest that eEF1A stimulates nuclear export of proteins from the cytoplasmic side of the nuclear envelope, without entering the nucleus. Together, these data identify a role for eEF1A, a cytoplasmic mediator of tRNA export in yeast, in the nuclear export of proteins in mammalian cells. These results also provide a link between the translational apparatus and subcellular trafficking machinery demonstrating that these two central pathways in basic metabolism can act cooperatively.
Khacho
Mireille
M
Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, K1H 8M5, Canada.
Mekhail
Karim
K
Pilon-Larose
Karine
K
Pause
Arnim
A
Côté
Jocelyn
J
Lee
Stephen
S
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D009685:Nuclear Envelope / Q000378:metabolism; D049790:Nuclear Export Signals / Q000235:genetics*; D020648:Peptide Elongation Factor 1 / Q000235:genetics / Q000378:metabolism*; D039122:Poly(A)-Binding Protein I / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000235:genetics / Q000378:metabolism
D049790:Nuclear Export Signals; D020648:Peptide Elongation Factor 1; D039122:Poly(A)-Binding Protein I; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D051794:Von Hippel-Lindau Tumor Suppressor Protein
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