Rad51 and Dmc1 Form Mixed Complexes Associated with Mouse Meiotic Chromosome Cores and Synaptonemal Complexes

Abstract

The eukaryotic RecA homologues RAD51 and DMC1 function in homology recognition and formation of joint-molecule recombination intermediates during yeast meiosis. The precise immunolocalization of these two proteins on the meiotic chromosomes of plants and animals has been complicated by their high degree of identity at the amino acid level. With antibodies that have been immunodepleted of cross-reactive epitopes, we demonstrate that RAD51 and DMC1 have identical distribution patterns in extracts of mouse spermatocytes in successive prophase I stages, suggesting coordinate functionality. Immunofluorescence and immunoelectron microscopy with these antibodies demonstrate colocalization of the two proteins on the meiotic chromosome cores at early prophase I. We also show that mouse RAD51 and DMC1 establish protein–protein interactions with each other and with the chromosome core component COR1(SCP3) in a two-hybrid system and in vitro binding analyses. These results suggest that the formation of a multiprotein recombination complex associated with the meiotic chromosome cores is essential for the development and fulfillment of the meiotic recombination process.

BRCA2: a universal recombinase regulator

“…These foci are thought to represent sites on chromatin where DNA repair reactions take place. Similarly, RAD51 forms foci on meiotic chromosomes, where it colocalizes with DMC1 (Barlow et al, 1997;Tarsounas et al, 1999). These foci appear similar to the RAD51 foci observed in somatic cells after DNA damage and presumably identify sites of meiotic recombination (Haaf et al, 1995;Raderschall et al, 1999).…”

Evolutionary history of the mammalian synaptonemal complex

“…This hypothesis is based on observations made in the electron microscope where LNs were seen in close contact to the CE of beetle spermatocytes (Schmekel and Daneholt 1998). Furthermore, the above described interactions between proteins of the homologous recombination machinery and SC components (Tarsounas et al 1999;Bolcun-Filas et al 2009) provide initial indications for a complex interaction network between the elements of these two meiotic features which might explain their tight interdependency. 2) Besides the reciprocal recombination of the DNA, the chromosomal axes also need to be exchanged to produce chiasmata.…”

“…Besides, different studies have reported about interactions between early proteins of the recombination machinery and SC components. In the first study, binding abilities of the recombinases RAD51 and DMC1 with SYCP3 and between RAD51 and SYCP1 could be detected in a yeast two-hybrid system (Tarsounas et al 1999). Furthermore, Syce1 -/-spermatocytes revealed a co-localization of RAD51 and SYCE2.…”

“…Additionally, the importance of the elongation complex might also be related to the process of homologous recombination. Indeed, SYCE2, SYCP1 and SYCP3 are the only components of the murine SC so far for which a direct interaction with the homologous recombination machinery -with RAD51 and DMC1 -was described (Tarsounas et al 1999;). RAD51 is highly conserved from mouse (RefSeq: NP_035364.1) to Hydra (RefSeq: XP_002169171.1) exhibiting a sequence identity of 82% in an alignment with BLAST.…”

“…TNs now localize between the LEs and contain proteins, such as RPA, MSH4, BLM helicase and topoisomerase, which are implicated in the resolution of most of the early DNA-DNA interactions (Moens et al 2002). Results from mice (Tarsounas et al 1999;Baudat et al 2000;Bolcun-Filas et al 2009) and from yeast (Storlazzi et al 1996;Agarwal and Roeder 2000) research further suggest that some recombination nodules at this stage may function as initiation sites for synapsis. At these sites, the assembly of the CR starts and spreads into both directions to connect the homologs over their entire length.…”