Date of Award
Doctor of Philosophy (PhD)
ING4 belongs to a family of proteins that have been implicated in tumor suppression and has been linked to the activation of p53 target genes in a p53- dependent manner. However the mechanism by which it interacts with p53 to activate transcription from these genes is unclear. In this study I use in vitro reconstitutions of cellular processes to biochemically dissect the activity of the ING4 complex, complementing the cell based assays that give a more physiological but less defined window into ING4’s effect on p53 transcriptional activity. Purification of the ING4 complex allowed verification of previously known subunits and identification of BRPF1/2/3 as a core ING4 component. Reconstitution of the ING4 complex allowed the identification of two distinct variants of the ING4 complex which utilized either JADE or BRPF as the central scaffold subunit. Both these variants were required to recapitulate the histone acetyltransferase activity of the endogenous complex. Using these complexes, I demonstrate that the ING4 complex histone modifying activity is not directly affected by p53 but is rather indirectly modulated through p53-dependent p300 activity and enhanced by the presence of the p53-dependent trimethylated H3K4 histone mark. I also establish an ING4 complex-mediated p53-dependent transcription system on chromatin templates and show that the ING4 complex has a direct effect on p53 dependent transcription. Additionally, the same conditions that enhance ING4 complex histone acetylation, namely p300 and trimethylated H3K4, also enhance the ING4 complex’ effects on p53 dependent transcription. Taken together, these results establish ING4 as a transcriptional coactivator of p53 and suggest two mechanisms by which p53 affects ING4 complex histone modification and transcriptional activity.
Bok, Jabez, "Mechanism of Action of ING4 as a Transcriptional Coactivator of p53" (2015). Student Theses and Dissertations. 275.