Repetitive DNA is common in the human genome. It is prone to length changes, expansions and contractions. These changes lead to genome instability that can cause disease. Huntington?s Disease (HD), Fragile X syndrome, and Amyotrophic Lateral Sclerosis (ALS) are examples of diseases caused by a repeat expansion. In addition to disease-causing expansions, DNA repeats are hotspots for chromosome fragility and rearrangements. Cancer cells exhibit increased fragility as well and chromosome rearrangements, thus a better understanding of repair fidelity within repetitive DNA could lead to insights into cancer etiology. We have established multiple assays for studying repeat instability and fragility using a yeast system, which can be manipulated genetically. Using these assays, we have shown that repair via homologous recombination (HR) is a significant source of CAG repeat expansions. Yeast cells containing an expanded repeat tract and lacking the strand annealing protein Rad52, required for homologous recombination, have high frequencies of chromosome fragility, cell cycle arrest, and cell death, further implicating HR as an important process in repeat maintenance. Moreover, we have identified a limited set of histone modifications that control the fidelity of repair within an expanded CAG repeat. There are several types of HR within cells, which can occur with different temporal and spatial locations. The HR event which is causing repeat expansions, and the cellular processes that control repair fidelity, are currently unclear. To fill these gaps in knowledge, we propose to develop, in collaboration with Jim Haber, controllable systems to induce HR within a repetitive DNA tract, in order to determine which types of HR repair generate repeat expansions. In addition, we will investigate how timing and location within the nucleus influence repair pathway choice and fidelity. Lastly, we will investigate how histone modifications control repair fidelity during homologous recombination, and, in collaboration with Sergei Mirkin, screen for additional factors that influence this process. The overall goal is to determine the mechanisms the cell uses to control repair fidelity and prevent expansions within repetitive DNA.

Public Health Relevance

Repeat expansions are the cause of over thirty inherited diseases, thus it is important to understand the mechanism by which such expansions occur. Because repeat length correlates with disease severity, interference with expansions or induction of contractions is a viable option for treatment. Knowledge of pathways that cause genomic instability also has relevance for cancer prevention and strategies for selectively targeting of cancer cells with defects in DNA repair.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Brandeis University
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Beagan, Kelly; McVey, Mitch (2016) Linking DNA polymerase theta structure and function in health and disease. Cell Mol Life Sci 73:603-15
Rodgers, Kasey; McVey, Mitch (2016) Error-Prone Repair of DNA Double-Strand Breaks. J Cell Physiol 231:15-24
Aksenova, Anna Y; Han, Gil; Shishkin, Alexander A et al. (2015) Expansion of Interstitial Telomeric Sequences in Yeast. Cell Rep 13:1545-51
Shah, Kartik A; Mirkin, Sergei M (2015) The hidden side of unstable DNA repeats: Mutagenesis at a distance. DNA Repair (Amst) 32:106-12
Kloosterman, Wigard P; Francioli, Laurent C; Hormozdiari, Fereydoun et al. (2015) Characteristics of de novo structural changes in the human genome. Genome Res 25:792-801
Haber, James E (2015) TOPping off meiosis. Mol Cell 57:577-81
Usdin, Karen; House, Nealia C M; Freudenreich, Catherine H (2015) Repeat instability during DNA repair: Insights from model systems. Crit Rev Biochem Mol Biol 50:142-67
Pandey, Shristi; Ogloblina, Anna M; Belotserkovskii, Boris P et al. (2015) Transcription blockage by stable H-DNA analogs in vitro. Nucleic Acids Res 43:6994-7004
Su, Xiaofeng A; Dion, Vincent; Gasser, Susan M et al. (2015) Regulation of recombination at yeast nuclear pores controls repair and triplet repeat stability. Genes Dev 29:1006-17
House, Nealia C M; Yang, Jiahui H; Walsh, Stephen C et al. (2014) NuA4 initiates dynamic histone H4 acetylation to promote high-fidelity sister chromatid recombination at postreplication gaps. Mol Cell 55:818-28

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