Homologous recombination plays a critical role in reductional segregation of chromosomes in meiosis. Meiotic recombination is initiated by the programmed induction of DNA double strand breaks (DSBs) and involves a mechanism related to recombinational repair of DSBs in mitotic cells. The key difference between meiotic and mitotic recombination is that the meiotic process must occur between homologous chromatids and the mitotic process usually occurs between sister chromatids. The central step of recombination is homologous strand invasion and exchange. This process is catalyzed by recombinases that are structurally and functionally related to the bacterial strand exchange protein, RecA. There are two RecA-like recombinases in most eukaryotic organisms, including budding yeast and humans;Rad51 is the only RecA-like recombinase involved in mitotic recombination. Dmc1 is a meiosis-specific recombinase that can function in the absence of Rad51, but often cooperates with it. In order to promote strand invasion, recombinases must first polymerize into helical filaments on the tracts of single strand DNA (ssDNA) that form at sites of DSBs. Accessory factors, called mediators, allow recombinase to displace single strand DNA binding proteins as they form filaments. Recent evidence indicates that a second type of accessory factor expends energy to promote dissociation of recombinases from DNA using ATP hydrolysis dependent DNA-translocase activity. The proposed work seeks to elucidate meiotic recombination in budding yeast.
The aims of this proposal are: 1. To visualize the architecture of the meiotic recombinosome using high-resolution light microscopy with the aim of determining if the previously detected side-by-side Rad51 and Dmc1 structures have a specific organization relative to the axes of the two chromosomes engaged in a recombination event. 2. To determine the mechanism underlying the functional differences between the DNA translocases Tid1/Rdh54 and Rad54. 3. To determine the mechanisms through which Dmc1's accessory factors interact to stimulate recombination. Defects in meiotic recombination cause chromosome non-disjunction and loss, both of which lead to birth defects and spontaneous abortion. Failure of recombinational repair in mitosis is implicated in the etiology of breast cancer and other malignancies.

Public Health Relevance

We will characterize the recombination machinery that exchanges chromosomes arms during meiosis. Meiosis forms eggs and sperm. Understanding recombination may prevent birth defects caused by errors in meiosis. Recombination prevents cancer in humans, so this work may improve cancer prevention and treatment.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Molecular Genetics B Study Section (MGB)
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Janes, Daniel E
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University of Chicago
Schools of Medicine
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Chan, Yuen-Ling; Zhang, Annie; Weissman, Benjamin P et al. (2018) RPA resolves conflicting activities of accessory proteins during reconstitution of Dmc1-mediated meiotic recombination. Nucleic Acids Res :
Gataulin, Daniil V; Carey, Jeffrey N; Li, Junya et al. (2018) The ATPase activity of E. coli RecA prevents accumulation of toxic complexes formed by erroneous binding to undamaged double stranded DNA. Nucleic Acids Res 46:9510-9523
Chan, Yuen-Ling; Bishop, Douglas K (2018) Purification of Saccharomyces cerevisiae Homologous Recombination Proteins Dmc1 and Rdh54/Tid1 and a Fluorescent D-Loop Assay. Methods Enzymol 600:307-320
Brown, M Scott; Grubb, Jennifer; Zhang, Annie et al. (2015) Small Rad51 and Dmc1 Complexes Often Co-occupy Both Ends of a Meiotic DNA Double Strand Break. PLoS Genet 11:e1005653
Joshi, Neeraj; Brown, M Scott; Bishop, Douglas K et al. (2015) Gradual implementation of the meiotic recombination program via checkpoint pathways controlled by global DSB levels. Mol Cell 57:797-811
Grubb, Jennifer; Brown, M Scott; Bishop, Douglas K (2015) Surface Spreading and Immunostaining of Yeast Chromosomes. J Vis Exp :e53081
Mason, Jennifer M; Dusad, Kritika; Wright, William Douglass et al. (2015) RAD54 family translocases counter genotoxic effects of RAD51 in human tumor cells. Nucleic Acids Res 43:3180-96
Shinohara, Miki; Hayashihara, Kayoko; Grubb, Jennifer T et al. (2015) DNA damage response clamp 9-1-1 promotes assembly of ZMM proteins for formation of crossovers and synaptonemal complex. J Cell Sci 128:1494-506
Chan, Yuen-Ling; Brown, M Scott; Qin, Daoming et al. (2014) The third exon of the budding yeast meiotic recombination gene HOP2 is required for calcium-dependent and recombinase Dmc1-specific stimulation of homologous strand assimilation. J Biol Chem 289:18076-86
Lao, Jessica P; Cloud, Veronica; Huang, Chu-Chun et al. (2013) Meiotic crossover control by concerted action of Rad51-Dmc1 in homolog template bias and robust homeostatic regulation. PLoS Genet 9:e1003978

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