BAF53, a component of chromatin remodelling and histone acetyltransferase complexes, has been shown to be essential for cell survival in human cells and plays roles in p53-mediated gene transcription. However, the mechanism concerned in the process needs to be further explored. In this study, we show that BAF53 is involved in the repression of p53-dependent p21-gene transcription by interacting with p53 both in vivo and in vitro. Through electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation analyses, we demonstrate that BAF53 can reduce the p53-binding ability to p21 promoter. By western-blot experiments, we find that BAF53 can decrease p53-Lys382 acetylation, which may be partially responsible for the repression of p53-binding ability. Furthermore, BAF53 represses p21-promoter activity in a BRG1-independent manner. These data contribute to elucidating the molecular mechanisms of BAF53 in regulating p53-mediated gene transcription.

c-Abl non-receptor tyrosine kinase has been implicated in many cellular processes including cell differentiation, stress response and regulating gene transcription. The mechanism by which c-Abl is involved in the regulation of gene transcription remains to be elucidated. In this study, we investigated the functions of c-Abl in the activation of p21 promoter. Our results showed that overexpression of c-Abl tyrosine kinase activated p21 promoter and endogenous p21 transcription in U2OS cells. We found that p53 is involved in the activation of p21 promoter by c-Abl, and integrative structure of p53 is required for regulating p21 transcription. In addition, the chromatin immunoprecipitation study demonstrated that c-Abl and p53 can be recruited to the region containing p53 binding site of p21 promoter, and c-Abl increases the DNA binding activity of p53 to the p21 promoter. Furthermore, not only the activation of p21 promoter but also the recruitment to p21 promoter by c-Abl is dependent on the interaction between c-Abl and p53 protein.