Kavi Mehta

Cells experience tens of thousands of DNA lesions per day that must be repaired to ensure that genetic stability is maintained. These lesions include strand breaks caused by exogenous and endogenous genotoxins. Endogenous sources include byproducts of metabolism such as reactive oxygen species and excess ribonucleotide triphosphate incorporation into DNA. Exogenous sources include industrial chemicals and oncogenic tumor viruses like human papilloma virus (HPV) that induce a range of lesions including mutagenic abasic sites, oxidative damage, strand-breaks, and bulky adducts. Lack of faithful repair leads to mutagenesis or genomic instability, causing developmental disorders, autoimmune diseases, cancers, and ageing. These diseases include all known cancers including colorectal cancers, head and neck cancers, cervical cancers, Systemic Lupus Erythematosus (SLE), and rare congenital diseases such as pediatric Aicardi Goutières. Many of these diseases disproportionately affect the most vulnerable communities such as the Hmong in Wisconsin due to both predisposition to these diseases and poor access to treatment.
I developed multiple methods to study stand-specific replication stress in human cells. These validated and powerful tools coupled with new high throughput pipelines to test mutagenic potential of leading and lagging strand stress in response to genotoxic agents provide a strong foundation for my laboratory’s overarching research plan goals.
Based on my results as an early-stage investigator, I hypothesize that lagging and leading specific lesions result in differential replication stress responses and mutagenesis because there are major differences between leading and lagging strand synthesis (continuous vs discontinuous synthesis). I will use the methods learned and developed during my postdoctoral training to determine how leading and lagging strand replication obstacles and viral insult generate differential mutagenic potential. These studies will answer important questions: Do major repair pathways or lesions influence mutagenic potential in a strand specific manner? Do error-prone translesion synthesis (TLS) polymerases operate on both replicating strands? Is mutagenesis more likely to occur on one strand and in what contexts is it most likely to occur? Are the strand specific replication stress responses different? Do environmental and endogenous genotoxins preferentially damage leading or lagging strands and what are the mutagenic consequences? Can therapeutic interventions be targeted to cancers with unique replication stress responses and profiles?
Answering these overarching questions and broadening the types of lesions that we study has the potential to discover new mechanisms of how mutations, genomic instability, and disease are induced or prevented to achieve my goal of being an outstanding world-class collaborative scientist and mentor while promoting the Wisconsin Idea and serving underserved populations.

How?

We will define factors required when cells encounter strand specific stress, the structure and biochemical kinetics involved, and the mutagenic consequences of strand specific obstacles. To date, few studies have been performed that investigate differences in the replication stress responses in this context.
Our research established several technical innovations including high-throughput and long-term physiological methods to assess the importance of replication stress response factors in protecting against genomic instability and mutagenesis. By combining these methods with an array of tools that I already developed with others such as, structural cryo-EM, biophysics based optical tweezer methodologies, high-throughput and unbiased iPOND (isolation of proteins on nascent DNA) screens, and CRISPR editing, we will demonstrate how DNA strand-specific obstacles influence mutagenesis and discover how the replisome is affected.