The transcriptional cofactor PCAF as mediator of the interplay between p53 and HIF-1 alpha and its role in the regulation of cellular energy metabolism

Constantinos Demonacos, Ramkumar Rajendran

    Research output: ThesisDoctoral Thesis


    Energy production is a very important function for the cells to maintain homeostasis, survive and proliferate. Cellular energy can be produced either through oxidative phosphorylation (OXPHOS) in the presence of oxygen or glycolysis in its absence. Cancer cells, even in the presence of oxygen prefer to produce energy through glycolysis and this confers them a survival advantage. Energy metabolism has recently attracted the interest of several laboratories as targeting the pathways for energy production in cancer cells could be an efficient anticancer treatment. For that purpose the role of various transcription factors in determining the pathway of energy production has been investigated extensively and there is evidence to suggest that oncogenic transcription factors promote glycolysis whereas tumour suppressors demote it. In line with this notion, the master regulator of cellular response to hypoxia, the Hypoxia Inducible Factor 1 (HIF-1) has been shown to induce the expression of a variety of genes encoding enzymes involved in glucose metabolism as well as OXPHOS favouring energy production through glucose metabolism in hypoxic cells. The tumour suppressor p53 on the other hand inhibits glycolysis and stimulates OXPHOS. One of the pathways through which p53 exerts these effects, is by inducing the inhibitor of glycolysis TIGAR and the cytochrome c oxidase assembly factor SCO2 gene expression under DNA damage conditions. However, the regulation of the expression of these genes in hypoxic conditions has been only partially elucidated. We hypothesised that under hypoxic conditions, TIGAR and SCO2 gene expression might be differentially regulated in cells bearing mutated p53 and in these cells the involvement of HIF-1 could be crucial. Indeed under hypoxia mimicking conditions, the TIGAR and SCO2 protein and mRNA levels were found to be modulated differentially in p53 wild type and mutant cell lines. The bioinformatics analysis revealed the presence of hypoxia responsive elements (HREs) within the regulatory region of the promoters of TIGAR and SCO2 genes. Firefly reporter assays and chromatin immunoprecipitation (ChIP) assays have indicated that HIF-1 plays a crucial role in the regulation of TIGAR gene expression. The direct involvement of HIF-1 in the regulation of SCO2 gene expression requires further investigation. We and others have recently reported that PCAF is a common cofactor for p53 and HIF-1α, regulating the protein stability and transcription target selectivity of both transcription factors thereby orchestrating the balance between life and death in cancer cells. We hypothesised that PCAF plays a similar role in the regulation of cellular energy metabolism by differentially targeting HIF-1α and p53 to the promoter of TIGAR and SCO2 genes. In this study we present evidence to support the notion that PCAF plays an import role in the regulation of TIGAR and SCO2 gene expression under hypoxic mimicking conditions. This conclusion was supported by assessing the functional consequences of PCAFwt and PCAFHAT overexpression on the intracellular lactate production, cellular oxygen consumption, NAD+/NADH ratio and ROS generation in cells under hypoxia mimicking conditions.
    Original languageEnglish
    Awarding Institution
    Publication statusPublished - Oct 2011


    • Transcription
    • acetylation
    • Energy metabolism
    • p53
    • HIF-1
    • PCAF
    • TIGAR
    • SCO2


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