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Cloning of a bcl-2 homologue by interaction with adenovirus E1B 19K
S N Farrow1, J H White, I Martinou
1Molecular Science Department, Glaxo Research and Development Ltd, Greenford, Middlesex, UK.
Abstract:
A number of DNA viruses carry apoptosis-inhibiting genes which enable the virus to escape from the host response. The adenovirus E1B 19K protein can inhibit apoptosis induced by E1A, tumour-necrosis factor-alpha, FAS antigen and nerve growth factor deprivation. The molecular basis of this inhibition remains poorly understood, but the fact that protection is seen in the absence of other viral proteins suggests that E1B 19K targets cellular proteins. We report here the identification of three cellular proteins that bind E1B 19K. One of these is a new member of the bcl-2 family, which we have called bak (for bcl-2 homologous antagonist/killer). This protein, which is expressed in a wide variety of cell types, binds to E1B 19K and to the Bcl-2 homologue Bcl-XL (ref. 17) in yeast. In addition, overexpression of bak in sympathetic neurons deprived of nerve growth factor accelerates apoptosis and blocks the protective effect of co-injected E1B 19K.
Insights
Adenovirus E1B 19K protein inhibits programmed cell death by targeting cellular proteins. A newly identified bcl-2 family member, bak, binds E1B 19K and accelerates apoptosis when overexpressed.
Area of Science:
- Molecular Biology
- Virology
- Cell Biology
Background:
- DNA viruses often encode apoptosis-inhibiting proteins to evade host immune responses.
- Adenovirus E1B 19K protein is known to suppress apoptosis triggered by various stimuli, including E1A and TNF-alpha.
- The precise molecular mechanisms underlying E1B 19K-mediated apoptosis inhibition are not fully elucidated.
Purpose of the Study:
- To identify cellular proteins that interact with the adenovirus E1B 19K protein.
- To characterize the function of these interacting proteins in apoptosis regulation.
- To understand the molecular basis of E1B 19K's anti-apoptotic activity.
Main Methods:
- Yeast two-hybrid screening to identify cellular binding partners of E1B 19K.
- Co-immunoprecipitation assays to confirm protein-protein interactions.
- Overexpression studies in neuronal cells to assess the role of identified proteins in apoptosis.
Main Results:
- Three cellular proteins were identified that bind to the adenovirus E1B 19K protein.
- One identified protein is a novel member of the bcl-2 family, designated bak (bcl-2 homologous antagonist/killer).
- Bak binds to both E1B 19K and Bcl-XL, and its overexpression in nerve growth factor-deprived neurons accelerates apoptosis and abrogates E1B 19K's protective effect.
Conclusions:
- The adenovirus E1B 19K protein interacts with cellular proteins, including the newly discovered bak protein.
- Bak, a pro-apoptotic member of the bcl-2 family, plays a role in regulating apoptosis and can be targeted by viral proteins.
- These findings provide insights into the molecular mechanisms by which adenovirus E1B 19K inhibits apoptosis, involving interaction with cellular death pathway components.