meiosis, homologous recombination, homology-directed DNA repair, gene targeting, Rad51, Dmc1, RecA
Homologous recombination repairs DNA damage, facilitates DNA replication, and creates the physical connections between chromosomes needed for reductional chromosome segregation during meiosis. We study two key recombination proteins, Dmc1 and Rad51 that are related to the central bacterial recombination protein, RecA. The mechanisms of recombinational repair of damage induced double strand breaks in DNA (DSBs) and the mechanism of meiotic recombination are very closely related in terms of the DNA intermediates that form; DSBs are normal intermediates in most or all meiotic recombination.
There are, however critical differences in how meiotic recombination is regulated as compared to mitotic recombinational repair. Our research is directed at understanding how Dmc1's function is specialized for meiosis, how the functions of Rad51 and Dmc1 differ, how the two proteins interact with one another during meiosis, and how the two proteins interact with components of the synaptonemal complex, a meiosis-specific chromosome scaffold. Our studies show that Rad51, which serves as the central “recombinase” in mitotic cells, is converted to a Dmc1 accessory protein in meiosis.
Our current approaches to understanding Rad51 and Dmc1 function include biochemical reconstitution of Dmc1 activity. This work currently involves 7 meiotic recombination proteins. We were first to show that recombination proteins can be detected at multiple subnuclear sites during recombination using immunostaining techniques. We have used cytological methods in the past to identify proteins required for recruitment of recombinase to double strand break sites in mitotic and meiotic cells. These regulators include the breast cancer susceptibility genes BRCA1 and BRCA2, which promote the assembly of recombination complexes, and RAD54 family translocases, which promote disassembly. We recently began to focus our cytological efforts on super-resolution light microscopy methods including STORM and STED. These methods are shedding new light on the architecture of the recombinosome. Finally we use molecular genetic techniques that allow detection of DNA recombination intermediates to study the mechanism that regulate meiotic recombination in living cells.