RecA homologs Dmc1 and Rad51 interact to form multiple nuclear complexes prior to meiotic chromosome synapsis

Dmc1 and Rad51, yeast homologs of the E. coli RecA protein, are shown by immunostaining to localize to as many as 64 sites within spread meiotic nuclei. Genetic requirements for this punctate pattern suggest it represents recombination intermediates. Dmc1 and Rad51 colocalize and are therefore likely to act together during recombination. Despite their similarities, the two proteins have specialized functions: Dmc1 complexes do not form in rad51 mutants, while Rad51 complexes are retained indefinitely in dmc1 mutants. Dmc1 and, by inference, Rad51 form complexes before synapsis as monitored by immunostaining for Zip1 protein. Analysis of zip1 mutants shows that Zip1 promotes dissociation of Dmc1 complexes. Colocalization of Dmc1 and Zip1 raises the possibility that Dmc1 and Rad51 are components of recombination nodules.