Importazole, a small molecule inhibitor of the transport receptor importin-β

ACS Chem Biol. 2011 Jul 15;6(7):700-8. doi: 10.1021/cb2000296. Epub 2011 Apr 21.


During interphase, the transport receptor importin-β carries cargoes into the nucleus, where RanGTP releases them. A similar mechanism operates in mitosis to generate a gradient of active spindle assembly factors around mitotic chromosomes. Importin-β and RanGTP have been implicated in additional cellular processes, but the precise roles of the Ran/importin-β pathway throughout the cell cycle remain poorly understood. We implemented a FRET-based, high-throughput small molecule screen for compounds that interfere with the interaction between RanGTP and importin-β and identified importazole, a 2,4-diaminoquinazoline. Importazole specifically blocks importin-β-mediated nuclear import both in Xenopus egg extracts and cultured cells, without disrupting transportin-mediated nuclear import or CRM1-mediated nuclear export. When added during mitosis, importazole impairs the release of an importin-β cargo FRET probe and causes both predicted and novel defects in spindle assembly. Together, these results indicate that importazole specifically inhibits the function of importin-β, likely by altering its interaction with RanGTP. Importazole is a valuable tool to evaluate the function of the importin-β/RanGTP pathway at specific stages during the cell cycle.

Publication types

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

MeSH terms

  • Active Transport, Cell Nucleus / drug effects
  • Animals
  • Cell Extracts
  • Female
  • Fluorescence Resonance Energy Transfer
  • GTPase-Activating Proteins / genetics
  • GTPase-Activating Proteins / metabolism
  • HeLa Cells
  • High-Throughput Screening Assays
  • Humans
  • Karyopherins / genetics
  • Karyopherins / metabolism
  • Mitosis / drug effects
  • NFATC Transcription Factors / genetics
  • NFATC Transcription Factors / metabolism
  • Ovum / drug effects
  • Ovum / metabolism
  • Quinazolines / pharmacology*
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Signal Transduction
  • Spindle Apparatus / drug effects
  • Xenopus
  • beta Karyopherins / antagonists & inhibitors*
  • beta Karyopherins / metabolism*
  • ran GTP-Binding Protein / genetics
  • ran GTP-Binding Protein / metabolism


  • Cell Extracts
  • GTPase-Activating Proteins
  • Karyopherins
  • NFATC Transcription Factors
  • Quinazolines
  • Receptors, Cytoplasmic and Nuclear
  • beta Karyopherins
  • exportin 1 protein
  • importazole
  • ran GTP-Binding Protein