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MDM2 inhibits p300-mediated p53 acetylation and activation by forming a ternary complex with the two proteins
1Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97201, USA.
Abstract:
p300 acetylates and activates the tumor suppressor p53 after DNA damage. Here, we show that MDM2, a negative-feedback regulator of p53, inhibited p300-mediated p53 acetylation by complexing with these two proteins. First, we purified a p300-MDM2-p53 protein complex from HeLa nuclear extracts, which was inactive in p53 acetylation, but active in histone acetylation. Also, wild-type, but not N-terminally deleted, MDM2 inhibited p53 acetylation by p300 in vitro and in vivo. This inhibition was specific for p53, because MDM2 did not affect acetylation of histones or the C terminus of p73 by p300. Consequently, wild-type, but not the mutant, MDM2 repressed the p300-stimulated sequence-specific DNA-binding and transcriptional activities of p53. These results demonstrate that an additional mechanism of p53 inactivation by MDM2 is to inhibit p53 acetylation by p300.
Insights
MDM2 inhibits p53 acetylation by p300, a key step in activating the tumor suppressor p53. This interaction, involving a p300-MDM2-p53 complex, represses p53
Area of Science:
- Molecular Biology
- Cancer Research
- Epigenetics
Background:
- p300 acetylates and activates the tumor suppressor p53 following DNA damage.
- MDM2 is a known negative-feedback regulator of p53.
- The interplay between p53, p300, and MDM2 in regulating p53 acetylation is not fully understood.
Purpose of the Study:
- To investigate the role of MDM2 in p300-mediated p53 acetylation.
- To elucidate the mechanism by which MDM2 affects p53 acetylation and activity.
Main Methods:
- Purification of a p300-MDM2-p53 protein complex from HeLa nuclear extracts.
- In vitro and in vivo assays to assess p53 acetylation by p300 in the presence of MDM2.
- Analysis of p53 DNA-binding and transcriptional activities.
Main Results:
- A purified p300-MDM2-p53 complex showed inhibited p53 acetylation but retained histone acetylation activity.
- Wild-type MDM2, but not an N-terminally deleted mutant, inhibited p53 acetylation by p300.
- MDM2 specifically inhibited p53 acetylation, not histone or p73 acetylation, and repressed p53 transcriptional activity.
Conclusions:
- MDM2 inhibits p53 acetylation by p300 through complex formation.
- This inhibition represents an additional mechanism for MDM2-mediated p53 inactivation.
- Understanding this interaction is crucial for cancer therapy development targeting the p53 pathway.