Mapping the indirect p53 gene regulatory network

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The transcription factor p53 serves as a central suppressor of tumor progression. It controls cell proliferation and apoptosis by regulating a plethora of target genes. However, it is not clear how p53 regulates many of its target genes, what factors besides p53 itself are necessary for up or downregulation and what their regulation contributes to a normal or cancer cell. Our incomplete picture of the molecular basis of p53-dependent gene regulation remains a critical gap to our overall understanding of tumor suppression.I propose that several pathways in the p53 gene regulatory network contribute independent, distinct and essential gene regulatory activities in response to p53 activation. To identify novel factors that mediate p53-dependent gene regulation, I will employ a novel meta-analysis approach that I developed earlier. Based on this approach, I identified a potential p53-p21-dependent switch from MYC-MAX to MAD-MAX promoter occupancy. To dissect the molecular mechanisms by which the transcription factors mediate p53-dependent gene regulation, we will use biochemical and genetic approaches. The goals of this proposal are to distinguish contributions of specific regulators that mediate p53-dependent transcriptional regulation and to determine their roles in tumor suppression.Aim 1: To determine the impact of candidate transcription factors, such as MYC/MAD/MAX, on p53-dependent gene regulation, we will employ a dual approach. We will identify high confidence target genes with the meta-analysis and perform experiments to determine the impact of differential transcription factor binding, the requirement for specific promoter elements and changes in cellular response.Aim 2: To systematically identify additional candidates, I will employ my meta-analysis approach and test what factors are enriched for binding p53 regulated genes independent of DREAM and p53 binding. Moreover, given the important role of mouse models in bridging the gap between basic and clinical research, I will determine conservation of candidate pathways mediating indirect p53-dependent gene regulation between human and mouse. I will identify high confidence target gene maps and determine overlaps and differences between the human and mouse gene lists. Together, the results will provide a better understanding on how multiple pathways work in concert to mediate p53-dependent gene regulation.This application seeks to challenge and shift current paradigms that form the basis of our understanding of p53 signaling pathways in growth suppression. A detailed molecular profile of p53-dependent transcriptional regulation will be developed and the consequences of perturbing indirect regulators will be determined. Achieving the goals of this proposal will clarify what factors mediate p53-dependent gene regulation and how they contribute to tumor suppression. Understanding how p53 suppresses tumor progression may identify novel therapeutic targets to control cell growth.