Eukaryotic chromosomal DNA replication is a process that is at once robust and vulnerable. It is accurate and able to withstand environmental stress, such as DNA damage and replication impediments, through a highly evolved checkpoint mechanism. Yet the very act of replication, if executed in an untimely or uncoordinated fashion, can give rise to genomic instability. My laboratory is interested in understanding the mechanisms of replication stress-induced genome instability in eukaryotes. We are particularly interested in how unprotected replication forks (junctions of replicated and unreplicated DNA) can lead to single-stranded DNA (ssDNA) and double strand break (DSB) formation.

We use the baker's yeast Saccharomyces cerevisiae as a model organism to develop new technologies to query the genome for instability. Among these we have devised a powerful method called Break-seq to map DSBs genome-wide. Using this approach we have identified a novel mechanism whereby replication inhibitors induce chromosome fragile sites (CFSs), which are non-random locations in the genome that are prone to DSB formation. CFSs are a fascinating cytogenetic phenomenon now widely implicated in a slew of human diseases ranging from neurological disorders to cancer. Our research suggests that each replication inhibitor not only impacts replication fork stability but also induces gene expression in a drug-specific manner through the "moon-lighting" functions of the drug beyond those in DNA replication. As a result, unscheduled conflicts between replication and transcription cause DSBs and chromosome fragility. Current projects in my lab are designed to test this hypothesis using a combination of biochemical and genetic approaches in both yeast and human cell lines.

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