The C-terminal region of Brh2 (Brh2 CT ), the BRCA2 homolog in Ustilago maydis, is highly conserved and aligns with the DSS1/DNA-binding domain (DBD) of mammalian BRCA2, while the N-terminal region (Brh2 NT ) is poorly conserved and has no obvious functional domain except for the single Rad51-interacting BRC element. Paradoxically, Brh2NT , but not Brh2 CT , complements the DNA repair and recombination deficiency of the brh2 mutant. We show here that Brh2NT exhibits an unexpected DNA binding activity with properties similar to that of the full-length protein. Deletion mapping localized the region responsible for the DNA binding activity to a stretch of residues between the BRC element and the canonical DBD. A heterologous DNA-binding domain from the large subunit of replication protein A substituted for the endogenous binding region within Brh2NT in supporting DNA repair. Rad51-promoted strand invasion was stimulated by Brh2NT , but required the presence of the BRC element. The findings suggest a model in which Brh2NT serves as the principal site for association with DNA, while the Brh2 CT provides a means for regulation.The repair of damaged DNA by homologous recombination is a high fidelity and universal process for maintaining genome integrity. At the heart of it is the use of an undamaged homologous DNA sequence as a template to direct repair of damaged regions. In eukaryotes, Rad51 plays the key role of promoting the search for the homologous sequence (1). Rad51 assembles into a complex with single-stranded (ss) 2 DNA that has been revealed after some processing of the damaged duplex to form a nucleoprotein filament, which is the active element for promoting homologous pairing and DNA strand exchange. BRCA2 is an important regulator of Rad51 activity (2, 3). Investigations using peptides or synthetic fusion proteins designed to model component elements of human BRCA2 suggest both positive and negative roles for BRCA2 in organizing Rad51 filaments (4 -8).Biochemical studies with Brh2, the BRCA2 homolog from the fungus Ustilago maydis, have demonstrated that it mediates Rad51 assembly on a protruding single-strand DNA tail (9). Interaction of Rad51 with Brh2 is through the single BRC element located in the N-terminal region of the protein (10). The BRC element comprises a sequence of about 30 amino acids (aa) that mimics a critical determinant of the Rad51 polymerization interface (11,12). Rad51 also interacts with Brh2 through a second, poorly defined locus, the CRE, located at the extreme C terminus of Brh2 (13). These N-terminal and C-terminal elements communicate with each other in some as yet unknown way to support proper Rad51 filament assembly. Such communication requires an interplay that is coordinated by Dss1 (13), a small versatile acidic protein that interacts with Brh2 in a region corresponding to a segment of the DSS1/DNAbinding domain (DBD) in mammalian BRCA2 (14). The mammalian BRCA2 DBD domain consists of a tandem array of three oligonucleotide/oligosaccharide-binding (OB) folds and a helix-r...