Interaction between Arabidopsis Brca2 and Its Partners Rad51, Dmc1, and Dss1

Abstract

The Arabidopsis (Arabidopsis thaliana) orthologs of Brca2, a protein whose mutations are involved in breast cancer in humans, were previously shown to be essential at meiosis. In an attempt to better understand the Brca2-interacting properties, we examined four partners of the two isoforms of Brca2 identified in Arabidopsis (AtRad51, AtDmc1, and two AtDss1 isoforms). The two Brca2 and the two Dss1 isoforms are named AtBrca2(IV), AtBrca2(V), AtDss1(I), and AtDss1(V) after their chromosomal localization. We first show that both AtBrca2 proteins can interact with either AtRad51 or AtDmc1 in vitro, and that the N-terminal region of AtBrca2 is responsible for these interactions. More specifically, the BRC motifs (so called because iterated in the Brca2 protein) in Brca2 are involved in these interactions: BRC motif number 2 (BRC2) alone can interact with AtDmc1, whereas BRC motif number 4 (BRC4) recognizes AtRad51. The human Rad51 and Dmc1 proteins themselves can interact with either the complete (HsRad51) or a shorter version of AtBrca2 (HsRad51 or HsDmc1) that comprises all four BRC motifs. We also identified two Arabidopsis isoforms of Dss1, another known partner of Brca2 in other organisms. Although all four Brca2 and Dss1 proteins are much conserved, AtBrca2(IV) interacts with only one of these AtDss1 proteins, whereas AtBrca2(V) interacts with both of them. Finally, we show for the first time that an AtBrca2 protein could bind two different partners at the same time: AtRad51 and AtDss1(I), or AtDmc1 and AtDss1(I).

BRCA2: a universal recombinase regulator

“…These interactions occur through the N-terminal BRC motif-containing region of BRCA2 (AtBRCA2(IV) 1-784 ). Interestingly, interactions with RAD51 were blocked by the presence of a polypeptide corresponding to the human BRC3 motif, while this peptide had no effect on AtBRCA2(IV)-AtDMC1 interactions (Dray et al, 2006). Furthermore, the BRC2 motif of AtBRCA2(IV) was found to interact with AtDMC1, whereas the binding to RAD51 was mediated through the BRC4 motif, indicating that the AtBRC motifs exhibit different specificities for the two recombinases (Dray et al, 2006).…”

“…Interestingly, interactions with RAD51 were blocked by the presence of a polypeptide corresponding to the human BRC3 motif, while this peptide had no effect on AtBRCA2(IV)-AtDMC1 interactions (Dray et al, 2006). Furthermore, the BRC2 motif of AtBRCA2(IV) was found to interact with AtDMC1, whereas the binding to RAD51 was mediated through the BRC4 motif, indicating that the AtBRC motifs exhibit different specificities for the two recombinases (Dray et al, 2006). Details of the interactions that take place between human BRCA2 and DMC1 protein were recently described (Thorslund et al, 2007).…”

Green Evolution and Dynamic Adaptations Revealed by Genomes of the Marine Picoeukaryotes Micromonas

“…In Arabidopsis, BRCA2 protein plays an essential role in meiosis, interacting with DMC1 and RAD51 (79). Furthermore, two paralogs of RAD54 were identified in each of the prasinophyte genomes.…”

Clarifying the mechanics of DNA strand exchange in meiotic recombination

“…The tumour suppressor protein Brca2 has also been implicated as a Rad51 mediator 44 . In many organisms, Brca2-deficient mutants have meiotic recombination defects [45][46][47][48] and, in plants at least, Brca2 and Dmc1 interact physically 46,49 .…”