PCAF is an HIF-1α cofactor that regulates p53 transcriptional activity in hypoxia

Abstract

The p53 tumour suppressor is involved in several crucial cellular functions including cell-cycle arrest and apoptosis. p53 stabilization occurs under hypoxic and DNA damage conditions. However, only in the latter scenario is stabilized p53 capable of inducing the expression of its pro-apoptotic targets. Here we present evidence that under hypoxia-mimicking conditions p53 acetylation is reduced to a greater extent at K320 site targeted by P300/ CBP-associated factor (PCAF) than at K382 site targeted by p300/CBP. The limited amounts of acetylated p53 at K320 are preferentially recruited to the promoter of the p21 WAF-1/CIP-1 gene, which appears to be unaffected by hypoxia, but are not recruited to the BID promoter and hence p53 is incapable of upregulating pro-apoptotic BID in hypoxic conditions. As the K320 p53 acetylation is the site predominantly affected in hypoxia, the PCAF histone acetyltransferase activity is the key regulator of the cellular fate modulated by p53 under these conditions. In addition, we provide evidence that PCAF acetylates hypoxia-inducible factor-1a (HIF-1a) in hypoxic conditions and that the acetylated HIF-1a is recruited to a particular subset of its targets. In conclusion, PCAF regulates the balance between cellcycle arrest and apoptosis in hypoxia by modulating the activity and protein stability of both p53 and HIF-1a.

MDM2 Regulates Hypoxic Hypoxia-inducible Factor 1α Stability in an E3 Ligase, Proteasome, and PTEN-Phosphatidylinositol 3-Kinase-AKT-dependent Manner

“…The function of HIF1␣ has been shown to be modulated through direct and indirect interaction with a number of proteins that regulate passage through the cell cycle including p53, MDM2 (murine double minute 2), E2F, and pRb (25)(26)(27)(28)(29). p53 has been shown to decrease the transcriptional activity of HIF1␣, in part through competition, in the setting of hypoxia, for binding to the transcriptional coactivators of both p53 and HIF1␣, p300 and PCAF (26).…”

Regulation of CXCR4 gene expression in breast cancer cells under diverse stress conditions

“…Quantitative reverse transcription PCR was performed as previously described (22). Briefly, total RNA was extracted from MCF-7 cells using the RNeasy kit (Qiagen), according to the manufacturer's instructions.…”

“…Cells were treated with 10 µM etoposide (Sigma-Aldrich) and 250 µM desferrioxamine (DSFX) (Sigma-Aldrich) for 16 h. Transient transfections were carried out using the Polyfect transfection reagent (Qiagen, Sussex, UK), according to the manufacturer's instructions. Constructs used for exogenous expression included HA-SRC-1 (29) Flag-SIRT-1 (Addgene, Cambridge, MA), pcDNA3 (22), and β-galactosidase (22). Human CXCR4 luciferase reporter containing 5 consensus HREs was constructed by amplifying the -1619 to -258 region (counted from the translation initiation site) and inserting it in the pGL3 promoter luciferase vector (Promega, USA).…”

“…The HIF-1α and p53 transcription factors interfere with each other's protein stability and transcriptional activity in hypoxic conditions (22)(23)(24). Previous work in our laboratory has indicated that the p300/CBP associated factor (PCAF) is a crucial coordinator of the action of both p53 and HIF-1α in hypoxic cancer cells (22).…”

“…Previous work in our laboratory has indicated that the p300/CBP associated factor (PCAF) is a crucial coordinator of the action of both p53 and HIF-1α in hypoxic cancer cells (22). PCAF, p300 and members of the p160 family of the nuclear hormone receptor (NR) co-activators, such as the steroid receptor co-activator 1 (SRC-1), bear intrinsic histone acetyl transferase (HAT) activity thereby modulating directly or indirectly the transcriptional activity of both HIF-1α and p53 (22,25,26). On the contrary, members of the NAD + -dependent deacetylase (HDAC) family of sirtuins, such as SIRT-1, antagonise HAT activity and target p53 and HIF-1α for deacetylation in mammalian cells (27).…”