p53PRISM: Regulation of life-and-death decisions by conformational switches

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The protein p53 guards against cancer by orchestrating the self-destruction of precancerous cells. Accordingly, p53 in most cancers ismalfunctioning and permits the unchecked cellular growth central to the disease. Understanding the molecular mechanismsunderlying p53's function is thus crucial, and researchers now know that p53 is regulated in part by a plethora of post-translationalmodifications (PTMs).In this project, I will investigate the functional consequences in p53 of an atypical PTM: the reorientation of a protein's backbone bythe isomerisation of a proline between cis and trans stereoisomers (Pro-Iso). Specifically, I hypothesise Pro-Iso acts as a"conformational switch" which drives p53 into distinct functional states. This hypothesis is untested due to the difficulty of obtainingchemically well-defined p53 variants and p53's recalcitrance towards structural biology techniques.To overcome these challenges, I will explore the role of Pro-Iso in p53's function via an interdisciplinary chemical biology andbiophysical approach. First, I will use the protein semisynthesis techniques pioneered by my supervisor Dr. Manuel Müller (King'sCollege London) to produce full-length p53 variants bearing precise chemical modifications that probe different aspects of Pro-Iso.Second, I will subject these variants to a host of biochemical assays to ascertain differences in key properties and functions. Finally, Iwill use single-molecule Förster resonance energy spectroscopy to investigate the effect of Pro-Iso on the conformational dynamicsunderlying p53's molecular interactions.This project will provide me with the transferable skills, training and track record needed to pursue a career as an independentresearch group leader. More importantly, this research will help further decode how p53 makes cellular life-and-death decisions andthus expand the knowledgebase from which global stakeholders seek to tackle growing cancer rates in an aging world.