title: Ubiquitination and proteasome-dependent degradation of human eukaryotic translation initiation factor 4E.
abstract: Translation initiation factor 4E (eIF4E) is a cytoplasmic cap-binding protein that is required for cap-dependent translation initiation. Here, we have shown that eIF4E is ubiquitinated primarily at Lys-159 and incubation of cells with a proteasome inhibitor leads to increased eIF4E levels, suggesting the proteasome-dependent proteolysis of ubiquitinated eIF4E. Ubiquitinated eIF4E retained its cap binding ability, whereas eIF4E phosphorylation and eIF4G binding were reduced by ubiquitination. The W73A mutant of eIF4E exhibited enhanced ubiquitination/degradation, and 4E-BP overexpression protected eIF4E from ubiquitination/degradation. Because heat shock or the expression of the carboxyl terminus of heat shock cognate protein 70-interacting protein (Chip) dramatically increased eIF4E ubiquitination, Chip may be at least one ubiquitin E3 ligase responsible for eIF4E ubiquitination.
authors.affiliation: Department of Viral Oncology, Institute for Virus Research, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Murata
authors.affiliation: Department of Viral Oncology, Institute for Virus Research, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan. Electronic address: kshimoto@virus.kyoto-u.ac.jp.
authors.forename: Kunitada
authors.initials: K
authors.lastname: Shimotohno
mesh_terms: D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D039561:Eukaryotic Initiation Factor-4E / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008239:Lysine / Q000737:chemistry; D009154:Mutation; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012315:RNA Caps / Q000737:chemistry; D012685:Sepharose / Q000737:chemistry; D025801:Ubiquitin / Q000737:chemistry*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D039561:Eukaryotic Initiation Factor-4E; D012315:RNA Caps; D025801:Ubiquitin; D012685:Sepharose; C467728:STUB1 protein, human; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; D008239:Lysine