Plays a critical role in homologous recombination repair (HRR) through its ability to recruit BRCA2 and RAD51 to DNA breaks. Strongly stimulates the DNA strand-invasion activity of RAD51, stabilizes the nucleoprotein filament against a disruptive BRC3-BRC4 polypeptide and helps RAD51 to overcome the suppressive effect of replication protein A (RPA). Functionally cooperates with RAD51AP1 in promoting of D-loop formation by RAD51. Serves as the molecular scaffold in the formation of the BRCA1-PALB2-BRCA2 complex which is essential for homologous recombination. Via its WD repeats is proposed to scaffold a HR complex containing RAD51C and BRCA2 which is thought to play a role in HR-mediated DNA repair. Essential partner of BRCA2 that promotes the localization and stability of BRCA2. Also enables its recombinational repair and checkpoint functions of BRCA2. May act by promoting stable association of BRCA2 with nuclear structures, allowing BRCA2 to escape the effects of proteasome-mediated degradation. Binds DNA with high affinity for D loop, which comprises single-stranded, double-stranded and branched DNA structures. May play a role in the extension step after strand invasion at replication-dependent DNA double-strand breaks; together with BRCA2 is involved in both POLH localization at collapsed replication forks and DNA polymerization activity (By similarity). Homooligomer; dissociated upon DNA damage thus allowing association with BRCA1. Oligomerization is essential for its focal accumulation at DNA breaks. Part of a BRCA complex containing BRCA1, BRCA2 and PALB2. Interacts with BRCA1 and this interaction is essential for its function in HRR. Interacts with RAD51AP1 and MORF4L1/MRG15. Component of the homologous recombination repair (HR) complex composed of ERCC5/XPG, BRCA2, PALB2, DSS1 and RAD51 (By similarity). Within the complex, interacts with ERCC5/XPG and BRCA2 (By similarity). Interacts with BRCA2, RAD51C, RAD51 and XRCC3; the interactions are direct and it may serve as a scaffold for a HR complex containing PALB2, BRCA2, RAD51C, RAD51 and XRCC3. Interacts with POLH; the interaction is direct (By similarity). Colocalizes with BRCA2 in nuclear foci. Interaction with BRCA2 occurs through a hydrophobic pocket at the crossover between WD repeats 4 and 5. The coiled coil domain mediates self-association. The chromatin-association motif (ChAM) mediates association with chromatin, probably through nucleosome core particles, independently from binding to D loop, ssDNA or dsDNA structures.