A cytomegalovirus-encoded inhibitor of apoptosis that suppresses caspase-8 activation

Proc Natl Acad Sci U S A. 2001 Jul 3;98(14):7829-34. doi: 10.1073/pnas.141108798. Epub 2001 Jun 26.


We have identified a human cytomegalovirus cell-death suppressor, denoted vICA, encoded by the viral UL36 gene. vICA inhibits Fas-mediated apoptosis by binding to the pro-domain of caspase-8 and preventing its activation. vICA does not share significant sequence homology with FLIPs or other known suppressors of apoptosis, suggesting that this protein represents a new class of cell-death suppressors. Notably, resistance to Fas-mediated apoptosis is delayed in fibroblasts infected with viruses that encode mutant vICA, suggesting that vICA suppresses death-receptor-induced cell death in the context of viral infection. Although vICA is dispensable for viral replication in vitro, the common targeting of caspase-8 activation by diverse herpesviruses argues for an important role for this antiapoptotic mechanism in the pathogenesis of viral infection in the host, most likely in avoiding immune clearance by cytotoxic lymphocytes and natural killer cells.

MeSH terms

  • Amino Acid Sequence
  • Apoptosis / genetics*
  • Caspase 8
  • Caspase 9
  • Caspases / genetics*
  • Cell Line
  • Cytomegalovirus / genetics*
  • Cytomegalovirus Infections / genetics*
  • Cytomegalovirus Infections / pathology*
  • Enzyme Activation / genetics
  • Gene Expression Regulation, Viral
  • Humans
  • Molecular Sequence Data
  • Signal Transduction / genetics
  • Viral Proteins / genetics*


  • UL36 protein, Human herpesvirus 1
  • Viral Proteins
  • CASP8 protein, human
  • CASP9 protein, human
  • Caspase 8
  • Caspase 9
  • Caspases