Replication of G-quadruplex DNA by translesion polymerases

All lifeforms depend on accurate replication and maintenance of their genome for growth, adaptation, and survival. Certain nucleic acid sequences rich in guanine can fold into four-stranded quadruplexes (G4) that present a natural barrier to DNA replication. These nucleic acid structures help control diverse cellular functions that drive evolution and affect the overall physiology and health of organisms. Additionally, G4 motifs play critical roles in human disease. For example, alterations in G4 regulatory processes contribute to neurological conditions, such as Alzheimer’s disease, Parkinson’s Disease, Amyotrophic Lateral Sclerosis/Frontal-temporal Dementia, and Fragile X syndrome. Dysregulation of G4 biology also impacts cancer in multiple ways, such as through activation of genes that promote tumor growth and survival. Even the natural process of aging is thought to depend to some degree on how reactive chemical species alter G4 motifs. The goal of this project is to determine how specific proteins are recruited to sites of replication and then function together to copy G4 DNA. The project will support scientific training of high school, undergraduate, and graduate students. and produce two main outcomes: (1) it will increase knowledge of molecular mechanisms that have evolved to maintain functionally important genomic regions across the tree of life and (2)help promote student performance and retention in biochemistry, molecular biology, and biomedical science programs. Plasticity in response to impaired fork progression is critical for bypass and tolerance of a variety of agents that challenge timely and accurate DNA replication. Translesion DNA synthesis (TLS) is an ancient mediator of the replication stress response. This project will elucidate the molecular and cellular features of Rev1 that led to the evolutionary selection of this TLS enzyme as a principle means of promoting successful resolution of G4 motifs. Both in vitro biochemical and biophysical techniques will be combined with cellular approaches to advance models describing the mechanics of Rev1-mediated G4 bypass and the importance of interactions with other replication proteins. The summation of the work will provide new insights that will advance models describing replication of difficult-to-replicate sequences that are conserved across species. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.