Acetylation of p53 augments its site-specific DNA binding both in vitro and in vivo

Abstract

p53 promotes tumor suppression through its ability to function as a transcriptional factor and is activated by posttranslational modifications that include acetylation. Our earlier study demonstrated that p53 acetylation can enhance its sequence-specific DNA binding in vitro, and this notion was later confirmed in several other studies. However, a recent study has reported that in vitro acetylation of p53 fails to stimulate its DNA binding to large DNA fragments, raising an important issue that requires further investigation. Here, we show that unacetylated p53 is able to bind weakly to its consensus site within the context of large DNA fragments, although it completely fails to bind the same site within short oligonucleotide probes. Strikingly, by using highly purified and fully acetylated p53 proteins obtained from cells, we show that acetylation of the C-terminal domain can dramatically enhance site-specific DNA binding on both short oligonucleotide probes and long DNA fragments. Moreover, endogenous p53 apparently can be fully acetylated in response to DNA damage when both histone deacetylase complex 1 (HDAC1)-and Sir2-mediated deacetylation are inhibited, indicating dynamic p53 acetylation and deacetylation events during the DNA damage response. Finally, we also show that acetylation of endogenous p53 indeed significantly augments its ability to bind an endogenous target gene and that p53 acetylation levels correlate well with p53-mediated transcriptional activation in vivo. Thus, our results clarify some of the confusion surrounding acetylation-mediated effects on p53 binding to DNA and suggest that acetylation of p53 in vivo may contribute, at least in part, to its transcriptional activation functions.ChIP ͉ transcription ͉ CBP͞p300

Transcriptional regulation by p53: one protein, many possibilities

“…In fact, in vitro and in vivo obtained data suggested that not only phosphorylation but CTD acetylation also enhances the sequence-specific DNA binding of p53. [49][50][51] This concept was also supported by the observation that deletion of the C-terminus increases its ability to bind to DNA using similar experimental conditions. The allosteric model was subsequently challenged by Anderson et al who showed that the interactions of p53 with PAb 421 or long DNA molecules had respectively stimulatory or inhibitory effects on its ability to bind to a short RE-containing oligonucleotide.…”

Mutant p53 gain of function can be at the root of dedifferentiation of human osteosarcoma MG63 cells into 3AB-OS cancer stem cells

“…It is well known that wild-type p53 is regulated by post-translational modifications as phosphorylation at Ser15 (required for its stabilization [50] and interaction with transcriptional co-activators) and acetylation at Lys320, 373 and 382 (required for both its transcriptional activity and its transcription-independent proapoptotic function [51,52]). Although it has been observed that in UV-induced mouse skin tumors mutp53 is phosphorylated at Ser15 and accumulated exclusively to the nucleus [53], up to now little is known about post-translational modifications of mutp53 in human OS cell lines or patients.…”

HDAC4 represses p21WAF1/Cip1 expression in human cancer cells through a Sp1-dependent, p53-independent mechanism

“…To date, the most common model for p21 WAF1/Cip1 repression in cancer cells is the recruitment of HDACs by Sp1/-Sp3 transcription factors in the proximal promoter region encompassing the Sp1/Sp3 binding sites, which in turn repress p21 WAF1/Cip1 transcription by deacetylating histones H3 and H4. However, a role for p53 in HDAC-associated p21 WAF1/Cip1 expression has also been reported in several human cancer cell lines (Lagger et al, 2003;Luo et al, 2004;Roy et al, 2005;Zhao et al, 2006).…”