An Acetylation Switch in p53 Mediates Holo-TFIID Recruitment

Abstract

Posttranslational modifications mediate important regulatory functions in biology. The acetylation of the p53 transcription factor, for example, promotes transcriptional activation of target genes including p21. Here we show that the acetylation of two lysine residues in p53 promotes recruitment of the TFIID subunit TAF1 to the p21 promoter through its bromodomains. UV irradiation of cells diacetylates p53 at lysines 373 and 382, which in turn recruits TAF1 to a distal p53-binding site on the p21 promoter prior to looping to the core promoter. Disruption of acetyl-p53/bromodomain interaction inhibits TAF1 recruitment to both the distal p53-binding site and the core promoter. Further, the TFIID subunits TAF4, TAF5, and TBP are detected on the core promoter prior to TAF1, suggesting that, upon DNA damage, distinct subunits of TFIID may be recruited separately to the p21 promoter and that the transcriptional activation depends on posttranslational modification of the p53 transcription factor.

Amino-terminal p53 mutations lead to expression of apoptosis proficient p47 and prognosticate better survival, but predispose to tumorigenesis

“…S4C), confirming an expected role of full-length p53 in the death process. Importantly, silencing of p47 expression in RKO −/− cells lead to a further consistent reduction of death, demonstrating that p47 (B and C) p53 null H1299 cells were transfected with selected ATp53 indels and analyzed by immunoblotting with an amino-terminal-specific p53 antibody (DO1) (recognizing amino acids [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], or an antibody that recognizes between residues 46-55 (Pab 1801) (B). One representative ATp53 indel, the 97delT, was mutated to substitute its methionines at amino acid 40 and/or 44 to alanine, and the plasmids were transfected similarly to analyze the expression of p47 (C).…”

“…To determine whether such mutations would affect fulllength p53 expression, we generated p53 cDNA constructs to mimic these mutations and expressed them in p53 null H1299 cells. Immunoblotting with the DO1 antibody that recognizes the amino terminus of p53 (amino acids [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] revealed the absence of any specific band in all of the cases tested (Fig. 1B).…”

“…In one case, phosphorylation on serine 46 has been shown to promote apoptotic target gene activation (25). Likewise, acetylation at K382 by p300, which binds to the amino terminus of p53, has been shown to regulate p21-like arrest gene activation (22). Thus, these data collectively indicate that modifications and cofactor binding on the amino terminus of p53 can have a profound effect on its functionality.…”

“…In this context, several studies have identified various cofactors required for selective transactivation of target genes involved in G 1 arrest (e.g., p21) and apoptosis (e.g., Pig3). One such example is TAF1, which was shown to be recruited to the p21 promoter and, hence, critical for its transactivation by p53 (22). Similarly, BRD7 was shown to bind to p53 and p300 and to be recruited to target gene promoters, affecting histone acetylation, p53 acetylation, and promoter activity of a subset of senescence target genes (23).…”

“…By contrast, full-length p53 was generally bound more significantly onto these promoters only after etoposide treatment, with weak basal binding noted in naïve conditions in RKO +/+ cells. Examination of cofactors recruited to the target promoters, such as TAF1 onto cell-cycle arrest promoters (22), or hCAS1 onto apoptotic promoters (24), revealed that while TAF1 was loaded efficiently upon etoposide treatment onto both the 5′ and 3′ p53-binding sites (referred to as p21A and p21B, respectively) on the p21 promoter in RKO +/+ cells, it was not the case in RKO −/− cells (Fig. 5E).…”