Site-specific acetylation of p53 directs selective transcription complex assembly

Histone deacetylase (HDAC) inhibitors are being investigated as possible adjuvant therapies for a number of diseases, including cancer. In addition to stabilization of acetylated histones, HDAC inhibitors stabilize the acetylation of a number of transcription factors, including p53. This study investigates the action of two HDAC inhibitors, CG-1521 and trichostatin A, which stabilize Ac-Lys-373 p53 and Ac-Lys-382 p53, respectively, in LNCaP prostate cancer cells. Real-time PCR demonstrates that CG-1521 induces p21 transcription whereas trichostatin A does not alter the steady state level of p21 mRNA. Co-immunoprecipitation demonstrates that the selective acetylation of p53 directs the recruitment of mutually exclusive coactivator complexes on the p53 response elements in the p21 promoter. Furthermore, the co-activator complexes initiate the recruitment of the components of the basal transcription apparatus to the basal promoter with markedly different outcomes because only Ac-Lys-373 p53 promotes the assembly of the basal transcriptional apparatus on the p21 promoter. These data highlight the profound effects of post-translational modification, including acetylation, on the function of p53. The data also suggest a novel and critically important role for protein acetylation/deacetylation in the assembly of active transcription processes that may be as important as classical phosphorylation/dephosphorylation.