title: The p53-induced factor Ei24 inhibits nuclear import through an importin β-binding-like domain.
abstract: The etoposide-induced protein Ei24 was initially identified as a p53-responsive, proapoptotic factor, but no clear function has been described. Here, we use a nonbiased proteomics approach to identify members of the importin (IMP) family of nuclear transporters as interactors of Ei24 and characterize an IMPβ-binding-like (IBBL) domain within Ei24. We show that Ei24 can bind specifically to IMPβ1 and IMPα2, but not other IMPs, and use a mutated IMPβ1 derivative to show that Ei24 binds to the same site on IMPβ1 as the IMPα IBB. Ectopic expression of Ei24 reduced the extent of IMPβ1- or IMPα/β1-dependent nuclear protein import specifically, whereas specific alanine substitutions within the IBBL abrogated this activity. Induction of endogenous Ei24 expression through etoposide treatment similarly inhibited nuclear import in a mouse embryonic fibroblast model. Thus, Ei24 can bind specifically to IMPβ1 and IMPα2 to impede their normal role in nuclear import, shedding new light on the cellular functions of Ei24 and its tumor suppressor role.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Kim G
authors.initials: KG
authors.lastname: Lieu
authors.forename: Eun-Hee
authors.initials: EH
authors.lastname: Shim
authors.forename: Jinling
authors.initials: J
authors.lastname: Wang
authors.forename: Ravi K
authors.initials: RK
authors.lastname: Lokareddy
authors.forename: Tao
authors.initials: T
authors.lastname: Tao
authors.forename: Gino
authors.initials: G
authors.lastname: Cingolani
authors.forename: Gerard P
authors.initials: GP
authors.lastname: Zambetti
authors.forename: David A
authors.initials: DA
authors.lastname: Jans
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D005047:Etoposide / Q000494:pharmacology; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D028901:alpha Karyopherins / Q000235:genetics / Q000378:metabolism; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism*; D020931:ran GTP-Binding Protein / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C402592:EI24 protein, human; C526185:EI24 protein, mouse; C424166:KPNB1 protein, human; C490631:Kpna2 protein, mouse; C094999:Kpnb1 protein, mouse; D009687:Nuclear Proteins; D010455:Peptides; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D028901:alpha Karyopherins; D028961:beta Karyopherins; C087978:karyopherin alpha 2; C015462:polyarginine; D005047:Etoposide; D020931:ran GTP-Binding Protein