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Deciphering Roles of Bloom Syndrome Helicase (Blm) in Genome Stability

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posted on 20.04.2020 by Evan B. Dewey, Jeff Sekelsky

DNA repair is critical to the maintenance and longevity of multicellular organisms. The DNA damage response provides a mechanism by which cells can respond to and correct damage accrued from damaging agents such as UV radiation, carcinogens, and other toxins. Without proper repair, cells can acquire mutations leading to improper function within tissues, genome instability, and cancer. While progress has been made in discovering the players and pathways involved in alleviating DNA damage, there is still more to understand about how these components function. One such regulator, Bloom Syndrome Helicase (Blm), is key to resolving both damage to DNA during replication, and in preventing detrimental “mitotic crossovers” (mitCOs) arising from homologous recombination, which can lead to loss of heterozygosity, genome instability, and cancer. My objectives are to characterize mitCO mechanisms, elucidate Blm function in resolving DNA damage during replication, and better understand Blm roles in cell cycle progression and tissue growth. I will define Blm function in resolving stalled replication forks by performing structure function mutations, examining fork and cell cycle progression to assess parts of Blm critical to DNA replication fidelity. I will identify types of DNA structures at stalled forks upon which Blm acts by performing a novel ChIP-EM assay, purifying Blm-bound fork structures from Drosophila embryos and visualizing them via Scanning Electron Microscopy. While loss of Blm is harmful to proper DNA repair, Blm is additionally overexpressed in many cancers, possibly to facilitate cancer cell growth and persistence. I will model Blm overexpression in Drosophila tissues, visualizing effects on cell cycle progression, tissue growth, and DNA repair in this context to understand potential Blm roles in cancer growth and persistence. Deciphering mitCO mechanisms and the functions of Blm in ensuring DNA replication fidelity, cell cycle progression, and tissue growth will lead to better understanding of DNA repair mechanisms and potential application of this knowledge toward cancer prevention and treatment.


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