Figure 6.

DSS1 and ssDNA disrupt BRCA2 multimers and stabilize BRCA2 monomers. The majority of BRCA2 multimers (including dimers) have a head-to-tail configuration featuring an N-to-C terminus interaction. Two SIRs at the N-terminus of BRCA2 form contacts with the third SIR on OB2 at the C-terminus of BRCA2. DSS1 and ssDNA could block this self-interaction synergistically and efficiently. A small population of BRCA2 multimers (including dimers) has a head-to-head configuration featuring an N-to-N terminus interaction. ssDNA counteracts this self-interaction, potentially by blocking the two SIRs at the N-terminus of BRCA2 in the proximity to the secondary N-terminal DNA-binding site. Large multimers of BRCA2 could be formed with both N-to-C and N-to-N configurations.