Expression of human BRCA2 in Saccharomyces cerevisiae complements the loss of RAD52 in double-strand break repair.

BRCA2 is a tumor-suppressor gene that is normally expressed in the breast and ovarian tissue of mammals. The BRCA2 protein mediates the repair of double-strand breaks (DSBs) using homologous recombination, which is a conserved pathway in eukaryotes. Women who express missense mutations in the BRCA2 gene are predisposed to an elevated lifetime risk for both breast cancer and ovarian cancer. In the present study, the efficiency of human BRCA2 (hBRCA2) in DSB repair was investigated in the budding yeast Saccharomyces cerevisiae. While budding yeast does not possess a true BRCA2 homolog, they have a potential functional homolog known as Rad52, which is an essential repair protein involved in mediating homologous recombination using the same mechanism as BRCA2 in humans. Therefore, to examine the functional overlap between Rad52 in yeast and hBRCA2, we expressed the wild-type hBRCA2 gene in budding yeast with or without Rad52 and monitored ionizing radiation resistance and DSB repair efficiency. We found that the expression of hBRCA2 in rad52 mutants increases both radiation resistance and DSB repair frequency compared to cells not expressing BRCA2. Specifically, BRCA2 improved the protection against ionizing radiation by at least 1.93-fold and the repair frequency by 6.1-fold. In addition, our results show that homology length influences repair efficiency in rad52 mutant cells, which impacts BRCA2 mediated repair of DSBs. This study provides evidence that S. cerevisiae could be used to monitor BRCA2 function, which can help in understanding the genetic consequences of BRCA2 variants and how they may contribute to cancer progression.

The Role of hBRCA2 in the Repair of Spontaneous and UV DNA Damage in Saccharomyces cerevisiae.

Women with mutations in the human BRCA2 gene ( hBRCA2 ) have an increased risk of developing breast and ovarian cancer throughout their lifetime. hBRCA2 transcribes proteins necessary for gene repair through homologous recombination (HR). In order to better understand the role of hBRCA2 in response to specific types of DNA damage, the present study evaluated HR in the budding yeast, Saccharomyces cerevisiae , using wildtype (WT) and rad52Δ mutant cells subject to spontaneous and UV damage in the presence or absence of hBRCA2. As expected, rad52Δ genotypes yielded lower recombination frequencies compared to WT in both spontaneous and UV exposure experiments. However, there was no significant difference between rad52Δ mutants with or without hBRCA2. Interestingly, higher UV exposure resulted in a relative increase in HR for only the rad52Δ mutant genotypes. The results demonstrate that hBRCA2 complementation may not be as substantial in spontaneous or UV DNA damage compared to double-strand break DNA damage, as previous work has shown.