Suppression of p53 Activity through the Cooperative Action of Ski and Histone Deacetylase SIRT1

Yasumichi Inoue,Shun-Ichiro Iemura,Tohru Natsume,Keiji Miyazawa,Takeshi Imamura

doi:10.1074/jbc.m110.177683

Abstract

Ski was originally identified as an oncogene based on the fact that Ski overexpression transformed chicken and quail embryo fibroblasts. Consistent with these proposed oncogenic roles, Ski is overexpressed in various human tumors. However, whether and how Ski functions in mammalian tumorigenesis has not been fully investigated. Here, we show that Ski interacts with p53 and attenuates the biological functions of p53. Ski overexpression attenuated p53-dependent transactivation, whereas Ski knockdown enhanced the transcriptional activity of p53. Interestingly, Ski bound to the histone deacetylase SIRT1 and stabilized p53-SIRT1 interaction to promote p53 deacetylation, which subsequently decreased the DNA binding activity of p53. Consistent with the ability of Ski to inactivate p53, overexpressing Ski desensitized cells to genotoxic drugs and Nutlin-3, a small-molecule antagonist of Mdm2 that stabilizes p53 and activates the p53 pathway, whereas knocking down Ski increased the cellular sensitivity to these agents. These results indicate that Ski negatively regulates p53 and suggest that the p53-Ski-SIRT1 axis is an attractive target for cancer therapy.

Highlights

Of various tumors [4]
The interaction between p53 and FLAG-Ski was minimally detected in unstressed cells because of the extremely low p53 levels. This interaction was strongly enhanced by treatment with low concentrations of actinomycin D (ActD), which activate a ribosomal stress response and stabilize the p53 protein (Fig. 1B) (30 –32)
Ski does not have deacetylase activity, Ski binds to the histone deacetylase SIRT1 and stabilizes the p53-SIRT1 interaction to promote p53 deacetylation, which subsequently decreases the DNA binding activity of p53

Summary

Introduction

Of various tumors [4]. Ski is thought to suppress TGF-␤ signaling primarily through transcriptional repression by recruiting the nuclear corepressor (N-CoR) and histone deacetylases to Smad complexes as well as inhibiting the recruitment of the transcriptional coactivator p300/CBP2 [5]. As the Ski fragment containing residues 76–304 is responsible for the ability of Ski to transform cells [36], we hypothesized that the ability of Ski to bind to p53 is important for the oncogenic activity of Ski. To map the Ski-binding domain in p53, we prepared various p53 deletion mutants (supplemental Fig. S1E) and examined the interaction between Ski and these p53 deletion mutants by immunoprecipitation/Western blot analyses.

Results

Conclusion