Figure 3.
BRCA1 requires wild-type p53 to activate p53-responsive elements. (A) 10.1Val5 mouse fibroblasts expressing temperature sensitive forms of murine p53 (wild type at 32°C and mutant at 39°C) were transfected with vector alone or BRCA1/pcDNA3 together with PGluc. Cells were transfected with the indicated DNA for 3 hr at 39°C, and were maintained at 32°C (lane 1 and 2) or 39°C (lane 3 and 4) for an additional 2 days before luciferase assay. Lanes: 1 and 3, pcDNA3 vector; 2 and 4, BRCA1/pcDNA3. (B) Primary fibroblasts prepared from p53 knockout mice were transfected and used for luciferase assays of PGluc. Approximately 2 × 106 p53 (+/+) cells (lane 1 and 2) or p53 (−/−) cells (lanes 3 to 6) were used for each of the assays. Lanes: 1 and 3, pcDNA3 vector; 2 and 5, BRCA1; 4, p53; 6, BRCA1 plus p53. Values shown here are the average of three or four independent experiments (A and B).