Fig. 1. p53 stimulates DNA BER in vitro. BER experiments with AP-DNA were performed as described in Materials and methods. Baculovirus-expressed purified p53 protein (200, 400, 800 ng) was added to BER reaction mixtures containing either purified APE and DNA pol β (A) or whole-cell extracts made from H1299 cells (B). As controls, the 21 bp U-DNA that was not treated with UDG [lane 1, (A)] and a 55 bp DNA that has a cytosine at the position of the uracil [lane 1, (B)] were used as templates. (C) Three hundred or 600 ng of bacterially expressed His-tagged p53 and p53 depletion mutants [p53 core domain (100–300), p53ΔC30 (1–363), p53ΔN96 (97–393) and the p53 C-terminus (300–393)] were added into reconstituted BER reaction mixtures. (D) Five hundred nanograms of each protein were run on an SDS gel, which was silver stained: full-length, lane 1; ΔN96, lane 2; ΔC30, lane 3; the core domain, lane 4; the C-terminus, lane 5. The numbers on the left show migration positions of the indicated molecular weight markers (in kDa) run in lane M.