53BP2 expression in cell lines containing wild-type or mutant p53. (A) The top panels show Western blots of lysates (30 μg of total protein per lane) prepared from human 041 and 087 LFS skin fibroblasts heterozygous for wild-type p53 (+/−) (lanes 2 and 4, respectively) or homozygous for p53 mutations (−/−) (lanes 3 and 5, respectively) and from normal primary human skin fibroblasts (GM38) homozygous for wild-type p53 (+/+) (lane 1). The fold differences, compared to GM38 cells, of 53BP2 protein normalized for tubulin are indicated below. 53BP2 protein was detected with monoclonal antibody DX547. The bottom panels show Northern blots of total RNA (15 μg/lane) prepared from cells as indicated above, probed for 53BP2, stripped, and reprobed for actin. The fold differences, compared to GM38 cells, of 53BP2 mRNA normalized for actin are indicated below. (B) Western blots of lysates (30 μg of total protein per lane) prepared from mouse fibroblasts homozygous for wild-type p53 (3T3, p21-null, and XPA+/−) or from p53 knockout mouse fibroblasts (p53-null). The fold differences, compared to 3T3 cells, of 53BP2 protein normalized for tubulin are indicated below. 53BP2 detected with rabbit antisera Rab-1.