Tid1 negatively regulates association of recombinase Dmc1 with chromatin when initiation of meiotic recombination is blocked.
Teresa M. Holzen (1), Parisha P. Shah (2), Heidi A. Olivares (3), Douglas K. Bishop (4)
(1) Committee on Genetics, University of Chicago, 920 E. 58th St., Chicago, IL, 60637, USA;
(2) Department of Molecular Genetics and Cell Biology;
(3) Department of Radiation and Cellular Oncology;
(4) Department of Radiation and Cellular Oncology, Committee on Genetics, Dept. of Molecular Genetics and Cell Biology
RecA homologs DMC1 and RAD51 are required for wild type (WT) levels of meiotic recombination. Two members of the SWI2/SNF2 group of chromatin remodeling factors, TID1/RDH54 and RAD54 act as accessory factors to the RecA homologs in biochemical assays, though the exact mechanism by which they enhance strand exchange activity in cells is unknown. Previous studies show Rad51-Dmc1 colocalize in subnuclear foci during meiotic recombination, and normal focus formation depends on the DNA double strand breaks (DSBs) that initiate recombination. Tid1 is required for high degrees of Rad51-Dmc1 colocalization in WT cells, suggesting Tid1 coordinates Rad51-Dmc1 assembly at DSBs. We now show that Tid1 blocks Dmc1 focus formation in the absence of DSBs. In a spo11 mutant lacking DSBs, Dmc1 focus formation is strongly defective. However, in a spo11 tid1 double mutant a larger fraction of nuclei form Dmc1 foci, which have staining intensity similar to those in WT nuclei. Chromatin IP experiments detecting association of Dmc1 at recombination hotspots suggest that the foci formed in spo11 tid1 mutants are not specific to recombination sites. We propose Tid1 promotes dissociation of Dmc1 from non-specific sites on chromatin to maintain a pool of Dmc1 available for recruitment to recombination complexes. Given Rad54's ability to dissociate Rad51 from dsDNA in vitro, Tid1 and Rad54 may share a function required for dynamic association/dissociation of Rad51 and Dmc1 with DNA.
Return to YGM 2004 Home at SGD