Nuclear localization signals of the BRCA2 protein

BRCA2 is a tumor suppressor gene whose germline mutations increase the life time risk of breast cancer. BRCA2 encodes a large nuclear protein involved in DNA repair, but the location of its functional domain has been unclear. Here, we report nuclear localization signals (NLSs) of the BRCA2 protein. B y expressing various portions of the BRCA2 protein tagged with enhanced gre en fluorescent protein in HeLa cells, we show that the C-terminal domain is necessary for nuclear localization. Two regions in the C-terminal domain w ere identified with functional NLSs by site-directed mutagenesis analyses. The NLSs locate between the germline mutation found in the most downstream position and the polymorphic stop codon, suggesting that defects in the pro per nuclear transport of the BRCA2 protein are causative of carcinogenesis. Our data thus provide a possible explanation for the high frequency of fra me-shift and nonsense mutations in BRCA2 of hereditary breast cancer patien ts. (C) 2000 Academic Press.