title: Translation initiation factor 4E (eIF4E) is regulated by cell death inhibitor, Diap1.
abstract: Translation initiation factor 4E (eIF4E) is a key regulator of protein synthesis. Abnormal regulation of eIF4E is closely linked to oncogenic transformation. Several regulatory mechanisms affecting eIF4E are discussed, including transcriptional regulation, phosphorylation and binding of an inhibitor protein. However it is not clear how the level of eIF4E protein is regulated under basal conditions. Here we demonstrate that Diap1 (Drosophila Inhibitor of Apoptosis Protein), a cell death inhibitor, binds directly to eIF4E and poly-ubiquitinates it via its E3 ligase activity, promoting its proteasome-dependent degradation. Expression of Diap1 caused a reduction of Cyclin D1 protein level and inhibited the growth stimulation induced by overexpression of eIF4E. Taken together, our results suggest that the level of eIF4E protein is regulated by Diap1, and that IAPs may play a role in cap-dependent translation by regulating the level of eIF4E protein.
authors.affiliation: Department of Life and Nanopharmaceutical Sciences, Kyung Hee University, Seoul 130-701, Korea.
authors.forename: Sun Kyung
authors.initials: SK
authors.lastname: Lee
authors.forename: Ji Sun
authors.initials: JS
authors.lastname: Lee
authors.forename: Ki Soon
authors.initials: KS
authors.lastname: Shin
authors.forename: Soon Ji
authors.initials: SJ
authors.lastname: Yoo
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000378:metabolism; D029721:Drosophila Proteins / Q000502:physiology*; D004331:Drosophila melanogaster; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism*; D051034:Inhibitor of Apoptosis Proteins / Q000502:physiology*; D054875:Ubiquitination
chemical_list: C111891:DIAP1 protein, Drosophila; D029721:Drosophila Proteins; D039561:Eukaryotic Initiation Factor-4E; D051034:Inhibitor of Apoptosis Proteins; D019938:Cyclin D1