Defining novel roles of the DNA repair factor REV7 in p53 signaling and regulation - PROJECT SUMMARY/ABSTRACT In the U.S. each year, over 600,000 patients die from cancer, and an estimated 2,000,000 new cases are diagnosed. Mutations in DNA damage response genes correlate with increased predisposition to cancer via chromosomal instability and aberrations. The DNA repair gene REV7 is an abundant, multifunctional protein. Recently our group described a novel role for REV7 in regulating the tumor suppressor p53. We also reported that p53 is highly stable in REV7 knockout cells, suggesting that REV7 promotes p53 protein destabilization. The mechanism of this interaction is unknown. Interestingly, some hotspot TP53 mutations identified in diverse cancers are associated with p53 overexpression and gain-of-function. Heightened p53 activity is also reported as a result of a germline TP53 mutation that underlies Li-Fraumeni Syndrome and confers an elevated risk of many cancers. Although p53 degradation has been well-studied, it is unclear why pathogenic p53 variants are stabilized in the cells. Given REV7’s role in p53 destabilization, we hypothesized that mutant p53 proteins do not effectively bind to REV7, leading to their accumulation within the cell. We will test our central hypothesis via the following Aims: SA1: Determine how REV7 regulates p53 protein destabilization. REV7 is a known participant in genome stability and tumor suppression. With four of our undergraduate students, we recently published important evidence that REV7 has novel functions in p53 activation and destabilization. However, the mechanistic details of REV7- mediated p53 regulation, both in the presence and absence of DNA damage, remain unclear. We will use biochemical approaches including genome editing to clarify how REV7 destabilizes p53 with/without DNA damage. This Aim will reveal a new regulatory mechanism for p53, a critical tumor suppressor. SA2: Determine how REV7 regulates p53 activity. We published that p53, p21, and MDM2 protein levels are increased in REV7 knockout cells. Furthermore, REV7 knockout cells significantly accumulate in G1 phase. It is unclear how REV7 is involved in the regulation of p53’s effector functions with/without DNA damage. We will use established molecular biology methods to determine how REV7 impacts p53 functions. We expect that our findings will establish REV7 as a negative regulator of p53 activity. Results from these studies are expected to clarify the role of REV7-mediated p53 regulation in cell cycle control, apoptosis, DNA repair, and other cellular processes. Given that p53 is a key tumor suppressor and “guardian of the genome,” defining the mechanistic interactions between REV7 and p53 has the potential to elucidate mechanisms of pathogenic gain-of-function in p53. This AREA project will offer hands-on investigative research opportunities to undergraduate and graduate students at UNC Charlotte, providing direct DNA-repair and cancer research training experience, while enhancing the research environment at a growing university.
