Collections > Electronic Theses and Dissertations > Analysis of the p53 Regulator MDM2 and the Identification of the Novel p53 Target Gene LRP1
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Available after 31 December, 2018

The transcription factor p53 responds to many stresses and regulates many different pathways. The earliest characterized functions of p53 include the induction of cell cycle arrest, apoptosis, and senescence; however, more recent studies have shown that p53 regulates other pathways, including lipid and glucose metabolism, DNA damage repair, and autophagy. While the activation of many of these pathways likely overlaps in many contexts, a current model proposes that p53 plays a critical role in deciding cell fate in response to stress. Indeed, depending on the type and severity of stress, p53 can induce genes that promote the resolution of cellular damage thereby allowing the cell to continue to proliferate, or p53 can induce genes that promote apoptosis to prevent the cell from propagating deleterious mutations. The chief negative regulators of p53, MDM2 and its homologous binding partner MDMX, are overexpressed in many cancers, especially those with wild-type p53. Although MDM2 and MDMX have been intensely studied, basic aspects regarding their interaction, such as how MDM2 preferentially heterooligomerizes with MDMX over homooligomerizing with MDM2, remain unknown. In my research, I generated multiple MDM2 mutant constructs to test their ability to homooligomerize with MDM2 and heterooligomerize with MDMX. Surprisingly, despite many studies suggesting that the C-terminal Really Interesting New Gene (RING) domain is critical for both MDM2 homooligomerization and MDM2-MDMX heterooligomerization, my results show that MDM2 RING structural mutations that prevent MDM2 enzymatic function and MDMX binding retain the ability to homooligomerize. Interestingly, deletion of the regulatory central acidic domain of MDM2 inhibits the ability of MDM2 to homooligomerize but does not impede its ability to heterooligomerize with MDMX, suggesting that MDM2-MDM2 homooligomerization and MDM2-MDMX heterooligomerization occur through different mechanisms. In another study, I identified the gene low-density lipoprotein receptor related protein 1 (LRP1) as a novel p53 target gene. Further analysis revealed that LRP1 protein induction occurs in response to sub-lethal but not lethal p53-activating stresses. Interestingly, although lethal p53-activating stress can induce LRP1 transcription, protein expression is impeded at the translational level. Collectively, these studies contribute to our knowledge of p53 regulation as well as the p53 regulome.