Interaction between the Product of the Breast Cancer Susceptibility Gene BRCA2 and DSS1, a Protein Functionally Conserved from Yeast to Mammals

Germ line mutations in the breast cancer susceptibility geneBRCA2 predispose to early-onset breast cancer, but the function of the nuclear protein encoded by the gene is ill defined. Using the yeast two-hybrid system with fragments of humanBRCA2 , we identified an interaction with the humanDSS1 (deleted in split hand/split foot) gene. Yeast and mammalian two-hybrid assays showed that DSS1 can associate with BRCA2 in the region of amino acids 2472 to 2957 in the C terminus of the protein. Using coimmunoprecipitation of epitope-taggedBRCA2 andDSS1 cDNA constructs transiently expressed in COS cells, we were able to demonstrate an association. Furthermore, endogenous BRCA2 could be coimmunoprecipitated with endogenous DSS1 in MCF7 cells, demonstrating an in vivo association. Apparent orthologues of the mammalianDSS1 gene were identified in the genome of the yeastsSchizosaccharomyces pombe andSaccharomyces cerevisiae . Yeast strains in which theseDSS1 -like genes were deleted showed a temperature-sensitive growth phenotype, which was analyzed by flow cytometry. This provides evidence for a link between theBRCA2 tumor suppressor gene and a gene required for completion of the cell cycle.