NSF-BSF: Studying the relationship between DNA replication and tandem repeat instability

Tufts University, Medford MA

Investigators

Abstract

Simple repetitive DNA sequences account for 3% of human genome. The length of individual DNA repeats can increase between generations, and this repeat expansion leads to over 50 hereditary human diseases, such as fragile X syndrome, Friedreich’s ataxia and Huntington’s disease. While each of these diseases is rare, altogether they affect one in several thousand newborns, making them a significant medical and societal burden. Thus, understanding the fundamental mechanisms of DNA repeat expansions is of prime importance. It is believed that repeats can occasionally lengthen during DNA replication, but the detailed mechanisms are poorly understood. This collaborative project between two research groups in the US and Israel combines cutting edge genetic and microscopy studies in a model experimental system to understand how repeat length changes during their replication. The project also creates cross-disciplinary training opportunities for graduate, undergraduate and high school students. Expansion of simple DNA repeats is a hallmark of numerous hereditary diseases in humans. This collaborative project between the Mirkin (Tufts University) and Aharoni (Ben-Gurion University of the Negev) laboratories aims to understand how replisome integrity ensures proper replication of simple DNA repeats and counteracts their instability. Using S. cerevisiae as a model organism, the project combines genetic assays that measure instability of various DNA repeats (e.g., expansions, contractions, and fragility), with single-cell live-microscopy analysis of replisome progression through these sequences. This dual approach will make it possible to resolve how a repeat’s length, its propensity to form dynamic DNA structures, and its orientation relative to the direction of replication affect progression of the fork. A particular emphasis of the project is on the role of coupling between leading and lagging strand syntheses and dNTP pool complexity in repeat instability. This collaborative US/Israel project is supported by the US National Science Foundation and the Israeli Binational Science Foundation. 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.