VIAF, a conserved inhibitor of apoptosis (IAP)-interacting factor that modulates caspase activation

John C. Wilkinson, Bettina W M Richter, Amanda S. Wilkinson, Ezra Burstein, Julie M. Rumble, Blerina Balliu, Colin S. Duckett

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Inhibitor of apoptosis (IAP) proteins are involved in the suppression of apoptosis, signal transduction, cell cycle control and gene regulation. Here we describe the cloning and characterization of viral IAP-associated factor (VIAF), a highly conserved, ubiquitously expressed phosphoprotein with limited homology to members of the phosducin family that associates with baculovirus Op-IAP. VIAF bound Op-IAP both in vitro and in intact cells, with each protein displaying a pre-dominantly cytoplasmic localization. VIAF lacks a consensus IAP binding motif, and overespression of VIAF failed to prevent Op-IAP from protecting human cells from a variety of apoptotic stimuli, suggesting that VIAF does not function as an IAP antagonist. VIAF was unable to directly inhibit caspase activation in vitro and a reduction of VIAF protein levels by RNA interference led to a decrease in Bax-mediated caspase activation, suggesting that VIAF functions to co-regulate the apoptotic cascade. Finally, VIAF is a substrate for ubiquitination mediated by Op-IAP. Thus, VIAF is a novel IAP-interacting factor that functions in caspase activation during apoptosis.

Original languageEnglish (US)
Pages (from-to)51091-51099
Number of pages9
JournalJournal of Biological Chemistry
Issue number49
StatePublished - Dec 3 2004

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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