The p53-induced factor Ei24 inhibits nuclear import through an importin β-binding-like domain

J Cell Biol. 2014 May 12;205(3):301-12. doi: 10.1083/jcb.201304055.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus
  • Amino Acid Sequence
  • Animals
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism*
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism*
  • Etoposide / pharmacology
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Mice
  • Molecular Sequence Data
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Peptides / metabolism
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Transfection
  • Tumor Suppressor Protein p53 / metabolism
  • alpha Karyopherins / genetics
  • alpha Karyopherins / metabolism
  • beta Karyopherins / genetics
  • beta Karyopherins / metabolism*
  • ran GTP-Binding Protein / metabolism

Substances

  • Apoptosis Regulatory Proteins
  • EI24 protein, human
  • EI24 protein, mouse
  • KPNB1 protein, human
  • Kpna2 protein, mouse
  • Kpnb1 protein, mouse
  • Nuclear Proteins
  • Peptides
  • TP53 protein, human
  • Tumor Suppressor Protein p53
  • alpha Karyopherins
  • beta Karyopherins
  • karyopherin alpha 2
  • polyarginine
  • Etoposide
  • ran GTP-Binding Protein