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AMF-1/Gps2 binds p300 and enhances its interaction with papillomavirus E2 proteins
Y C Peng1, D E Breiding, F Sverdrup
1Department of Dermatology, New England Medical Center, Tufts University School of Medicine, Boston, MA 02111, USA.
Abstract:
The cellular protein AMF-1 (Gps2) positively modulates gene expression by the papillomavirus E2 protein (D. E. Breiding et al., Mol. Cell. Biol. 17:7208-7219, 1997). We show here that AMF-1 also binds the transcriptional coactivator p300 in vitro and in vivo. E2 interacted weakly with p300. These observations led to a model in which AMF-1 recruits p300 into a complex with E2. Cotransfection of AMF-1 or p300 stimulated levels of E2-dependent transcription, while cotransfection of both AMF-1 and p300 showed an additive effect. The functional significance of p300 recruitment for E2 transactivation was evidenced by repression of E2-activated transcription by adenovirus E1A, which inhibits both coactivator and acetylase activities of p300. Antibodies to AMF-1 or E2 immunoprecipitated histone acetylase activity from cell lysates. Western blotting using antibody against acetyl-lysine failed to detect acetylation of AMF-1 or E2 in complex with p300. These results suggest that AMF-1 facilitates the recruitment of p300 and its histone acetylase activity into complexes with E2 and represents a novel mechanism of transcriptional activation.
Insights
The cellular protein AMF-1 recruits the coactivator p300 to papillomavirus E2 protein, enhancing gene expression. This interaction, involving p300
Area of Science:
- Molecular Biology
- Gene Regulation
- Virology
Background:
- The cellular protein AMF-1 (Gps2) is known to positively modulate gene expression mediated by the papillomavirus E2 protein.
- Papillomavirus E2 protein plays a crucial role in viral gene expression and replication.
Purpose of the Study:
- To investigate the interaction between AMF-1 and the transcriptional coactivator p300.
- To elucidate the mechanism by which AMF-1 influences E2-dependent transcription.
- To explore the role of p300 recruitment in E2 transactivation.
Main Methods:
- In vitro and in vivo binding assays to assess protein-protein interactions.
- Cotransfection experiments to evaluate the effect of AMF-1 and p300 on E2-dependent transcription.
- Adenovirus E1A repression assays to confirm the functional significance of p300.
- Immunoprecipitation and Western blotting to detect histone acetylase activity and protein acetylation.
Main Results:
- AMF-1 binds to the transcriptional coactivator p300 both in vitro and in vivo.
- AMF-1 facilitates the recruitment of p300 into a complex with the papillomavirus E2 protein.
- Cotransfection with AMF-1 or p300 individually stimulated E2-dependent transcription, with an additive effect when both were present.
- Adenovirus E1A repressed E2-activated transcription, highlighting the importance of p300's coactivator and acetylase functions.
- Histone acetylase activity was immunoprecipitated with AMF-1 or E2, but AMF-1 and E2 themselves were not acetylated in complex with p300.
Conclusions:
- AMF-1 acts as a crucial mediator, recruiting p300 and its associated histone acetylase activity to papillomavirus E2 protein complexes.
- This recruitment mechanism represents a novel pathway for transcriptional activation mediated by viral proteins.
- The findings provide new insights into the regulation of gene expression by viral oncoproteins and cellular coactivators.