Grant: Project Grant

Cancer is a leading cause of death worldwide. One hallmark of cancer cells is a high frequency of mutations and DNA rearrangements, collectively known as genome instability. Persistent DNA damage fuels genome instability and paradoxically, genomes are constantly exposed to a plethora of DNA-damaging agents. Cells use sophisticated pathways to repair DNA damage and preserve genome integrity. Determining how these pathways operate is a top priority for foundational and translational scientists. Most DNA repair pathways require nucleases to cut and remove damaged or abnormal DNA structures. However, without tight regulatory mechanisms, nucleases can catalyze catastrophic chromosome cleavage. There is burgeoning interest in leveraging this activity to sensitive cancer cells to anti-cancer drugs. Understanding how DNA nucleases recognize and cleave their DNA substrates will identify novel targets for therapeutic intervention. My research addresses these questions through the SMX tri-nuclease, which contains three nucleases, SLX1, MUS81-EME1 and XPF-ERCC1, bound to the SLX4 scaffold. Cells rely on SMX for accurate DNA repair and genome stability, although its untimely activation triggers chromosome pulverization. My research has defined mechanisms of SMX assembly and activation. Remarkably, MUS81-EME1 is responsible for most of the nuclease activities ascribed to SMX. We discovered a non-catalytic domain in MUS81 as the linchpin for targeted recognition of abnormal DNA structures (substrate specificity). We will use biochemical and cellular approaches to determine how this domain controls MUS81-EME1's substrate specificity and elucidate the biological consequences of relaxed substrate specificity in different cellular contexts. These studies will significantly advance our understanding of how MUS81-EME1 safeguards genome integrity. Likewise, our research will provide a solid framework for future research aimed at identifying compounds that target MUS81 in cancer cells.