Fig. 5.

BRCA2 variants and polypeptide fusions to assess the function of the BRC repeats in T. brucei recombination and VSG switching. A. Functional domains of BRCA2 variants and polypeptide fusions analysed by expression in bloodstream stage brca2−/− mutants are shown. Full-length T. brucei BRCA2 may contain up to 15 BRC repeats, a conserved DSS1-DNA-binding domain (DBD) and two putative nuclear localization signals (NLSs). T. vivax BRCA2 displays conservation of the DBD, but has only one BRC repeat and NLSs have not been predicted. 1BRC differs from full-length T. brucei BRCA2 only in reduction of the BRC array to a single repeat. BRCrep is a polypeptide fragment of T. brucei BRCA2 encompassing the BRC repeats and 33 downstream amino acids, including a bipartite NLS. BRC–RPA is a fusion of the BRCrep polypeptide to the 50 kDa T. brucei replication protein A subunit. B. Homologous recombination efficiency was assayed by determining the number of transformants recovered (per 10⁶ cells put on antibiotic selection) when the construct tub-HYG-tub was electroporated into wild-type (WT) cells, brca2−/− mutants and −/− cells expressing the BRCA2 variant polypeptides detailed above (−/−/+). C. VSG-switching frequencies of WT (Lister 427) T. brucei cells, brca2−/− mutants and −/− cells expressing the BRCA2 variant polypeptides are shown. Values are the means of at least three independent experiments, and bars represent standard error.