Mechanism of Dmc1-mediated Meiotic Recombination in Budding Yeast

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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. Meiotic recombination is subject to unique regulatory processes that promote recombination between homologous chromatids rather than sister chromatids and also regulate the frequency of crossover type recombination events to ensure all homologous chromosome pairs engage in at least one such event. The central step of recombination is homologous strand invasion and exchange. Budding yeast and many other organisms including humans have a specialized meiotic recombinase, Dmc1, that catalyzes the central step of meiotic recombination which involves DNA sequence homology searching that culminates in DNA strand exchange to form regions of hybrid DNA that connect recombining partners. A different strand exchange protein, Rad51, catalyzes the central step of mitotic recombination. Dmc1 has a unique set of meiosis-specific accessory proteins, but is also regulated by mitotic recombination proteins, including the mitotic recombinase Rad51. Rad51 is converted from an enzyme in mitosis into to a Dmc1 accessory protein during meiosis. Our group studies the molecular mechanism through which Dmc1 promotes meiotic recombination. We seek to understand how Dmc1’s activity is regulated by each of its accessory proteins. This goal is achieved by combining a wide range of advanced experimental approaches. Of particular importance is our group’s unique effort to biochemically reconstitute the recombination process using purified components. To complement our biochemical studies, we were first to develop the tools and methods required to study the architecture and dynamics of meiotic recombinosomes using super-resolution light microscopy. Our group also employs molecular genetic techniques that allow detection of broken and branched DNA recombination intermediates, as well as the protein-protein interactions that occur during the recombination process. We seek to combine these approaches to uncover important mechanistic features of the recombination process including the regulatory mechanisms that control it.