Related Experiment Videos
Adenovirus E1B 55-kilodalton oncoprotein inhibits p53 acetylation by PCAF
Y Liu1, A L Colosimo, X J Yang
1Department of Microbiology and Infectious Diseases, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada.
Abstract:
The adenovirus E1B 55-kDa protein binds to cellular tumor suppressor p53 and inactivates its transcriptional transactivation function. p53 transactivation activity is dependent upon its ability to bind to specific DNA sequences near the promoters of its target genes. It was shown recently that p53 is acetylated by transcriptional coactivators p300, CREB bidning protein (CBP), and PCAF and that acetylation of p53 by these proteins enhances p53 sequence-specific DNA binding. Here we show that the E1B 55-kDa protein specifically inhibits p53 acetylation by PCAF in vivo and in vitro, while acetylation of histones and PCAF autoacetylation is not affected. Furthermore, the DNA-binding activity of p53 is diminished in cells expressing the E1B 55-kDa protein. PCAF binds to the E1B 55-kDa protein and to a region near the C terminus of p53 encompassing Lys-320, the specific PCAF acetylation site. We further show that the E1B 55-kDa protein interferes with the physical interaction between PCAF and p53, suggesting that the E1B 55-kDa protein inhibits PCAF acetylase function on p53 by preventing enzyme-substrate interaction. These results underscore the importance of p53 acetylation for its function and suggest that inhibition of p53 acetylation by viral oncoproteins prevent its activation, thereby contributing to viral transformation.
Insights
Adenovirus E1B protein prevents tumor suppressor p53 acetylation by PCAF, inhibiting DNA binding. This viral oncoprotein interaction disrupts p53 function, aiding viral transformation.
Area of Science:
- Molecular Biology
- Virology
- Cancer Research
Background:
- The tumor suppressor p53 is crucial for cellular defense against DNA damage and oncogenic stress.
- p53's transcriptional activity, essential for its tumor-suppressive function, is regulated by post-translational modifications like acetylation.
- Acetylation by coactivators such as p300, CREB binding protein (CBP), and PCAF enhances p53's DNA binding and transcriptional activity.
Purpose of the Study:
- To investigate the mechanism by which the adenovirus E1B 55-kDa protein interacts with and affects p53 acetylation.
- To determine if the E1B 55-kDa protein specifically inhibits p53 acetylation by PCAF and its impact on p53 DNA-binding activity.
Main Methods:
- In vivo and in vitro acetylation assays to assess p53 acetylation by PCAF in the presence of E1B 55-kDa protein.
- DNA-binding assays to evaluate the effect of E1B 55-kDa protein expression on p53's sequence-specific DNA binding.
- Co-immunoprecipitation assays to examine the physical interaction between PCAF, p53, and the E1B 55-kDa protein.
Main Results:
- Adenovirus E1B 55-kDa protein specifically inhibits p53 acetylation by PCAF, both in vivo and in vitro.
- Histone acetylation and PCAF autoacetylation remain unaffected by the E1B 55-kDa protein.
- p53 DNA-binding activity is significantly reduced in cells expressing the E1B 55-kDa protein.
- The E1B 55-kDa protein binds to PCAF and a region of p53 (Lys-320) crucial for PCAF-mediated acetylation.
- The E1B 55-kDa protein interferes with the physical interaction between PCAF and p53, blocking PCAF's acetylase function on p53.
Conclusions:
- The adenovirus E1B 55-kDa protein directly inhibits p53 acetylation by PCAF by preventing enzyme-substrate interaction.
- This inhibition of p53 acetylation by a viral oncoprotein impairs p53's DNA-binding activity and transcriptional function.
- Disruption of p53 acetylation and function by viral proteins is a key mechanism contributing to viral-mediated cellular transformation.