Related Experiment Videos
Suppression of interleukin-1beta converting enzyme (ICE)-induced apoptosis by SV40 large T antigen
1Cardiovascular Research Center, Massachusetts General Hospital-East, Charlestown 02129, USA.
Abstract:
The Interleukin-1beta converting enzyme (ICE) family of proteins, homologs of the C elegans cell death gene product CED-3, play important roles in controlling vertebrate programmed cell death. Because inhibition of apoptosis may be an essential step in tumorigenesis, we investigated the interaction of the simian virus 40 large T antigen (T ag) with the ICE family. COS-1 cells which were transformed by the simian virus 40 do not die when transfected with expression constructs of Ice or Ich-1(L). We found that expression of T ag alone significantly prevents the ICE-induced apoptosis. p53, but not pRb or p107, antagonizes the effect of T ag on the suppression of ICE-induced cell death, but not on ICH-1(L)-mediated cell death. Thus, wild type p53 may potentiate ICE-induced apoptosis. Expression of a temperature sensitive mutant p53Val(135) sensitizes COS-1 cells to apoptosis induced by ICE at permissive but not at non-permissive temperature. While induction of bax, p21(WAF1/CIP), or cyclin D1 gene expression is observed in the COS-1 p53Val(135) cells at the permissive temperature, overexpression of bax, but not p21(WAF1/CIP) or cyclin D1, potentiates ICE-induced COS-1 cell death. Taken together, these results suggest that T ag may modulate the cells' susceptibility to death by suppressing activity of the ICE family through inhibiting p53.
Insights
Simian virus 40 large T antigen (T ag) inhibits programmed cell death by suppressing the Interleukin-1beta converting enzyme (ICE) family. Wild-type p53 may enhance ICE-induced apoptosis, while T ag inhibits this effect.
Area of Science:
- Molecular Biology
- Cell Biology
- Virology
Background:
- The Interleukin-1beta converting enzyme (ICE) family, homologs of CED-3, are crucial regulators of programmed cell death in vertebrates.
- Apoptosis inhibition is a key factor in tumorigenesis.
- The role of simian virus 40 large T antigen (T ag) in modulating apoptosis via the ICE family is not well understood.
Purpose of the Study:
- To investigate the interaction between simian virus 40 large T antigen (T ag) and the ICE family of proteins.
- To determine how T ag affects ICE-induced apoptosis.
- To elucidate the role of p53 in T ag-mediated suppression of apoptosis.
Main Methods:
- Transfection of COS-1 cells with expression constructs for T ag, ICE, and Ich-1(L).
- Assessment of apoptosis induction and inhibition.
- Analysis of p53's interaction with T ag and its effect on ICE-induced cell death.
- Expression analysis of bax, p21(WAF1/CIP), and cyclin D1 in cells with temperature-sensitive p53 mutant.
Main Results:
- Simian virus 40 large T antigen (T ag) expression significantly prevents ICE-induced apoptosis in COS-1 cells.
- Wild-type p53 antagonizes T ag's suppression of ICE-induced cell death, suggesting p53 potentiates ICE-induced apoptosis.
- A temperature-sensitive p53 mutant sensitizes cells to ICE-induced apoptosis at permissive temperatures, with bax overexpression enhancing this effect.
Conclusions:
- Simian virus 40 large T antigen (T ag) modulates cellular susceptibility to apoptosis by suppressing ICE family activity.
- T ag's inhibition of apoptosis appears to be mediated through the suppression of p53.
- These findings provide insights into viral protein interactions with host cell death pathways, relevant to cancer research.