The Recombination Mediator BRCA2: Architectural Plasticity of Recombination Intermediates Revealed by Single-Molecule Imaging (SFM/TIRF).

Cellular functions are defined by dynamic assembly, rearrangement, and disassembly of biomolecules to achieve control and specificity. As an example, effective DNA repair is brought about by the concerted action of several DNA processing proteins. Both changes in the structure of individual proteins and in the arrangement of multiple proteins together (referred to here as architecture) are inherent to biological function. These dynamic changes are exemplified in the breast cancer susceptibility protein 2 (BRCA2). BRCA2 is a DNA repair protein that undergoes changes in its own structure and affects changes in molecular architecture with partners during homologous recombination (HR) repair of DNA double strand breaks. These challenging features of BRCA2 protein, its size and predicted stretches of intrinsically disordered regions, have made it difficult to determine the structural consequences and mechanistic importance of interactions between full-length BRCA2 with RAD51 and other HR proteins. In this chapter, we describe scanning force microscopy (SFM)-based approaches to study DNA-protein complexes involved in HR, the architectural plasticity of full-length BRCA2, and the dynamic reorganization of these molecular components associated with essential steps of HR.