FIG. 4.
SV40 T-Ag inhibits p53 exonuclease activity. High Five insect cells were infected with recombinant baculovirus coding for the p531-320 fragment or SV40 T-Ag. Cells were lysed at 44 h pi, and the p531-320-containing lysate was split. One half was purified by metal affinity chromatography, and the other half was mixed with SV40 T-Ag-containing lysate and also purified for His-tagged p531-320 by metal affinity chromatography. Column fractions of both preparations were analyzed by SDS-PAGE (B, panels a and b) and Western blotting (A) and tested for exonuclease activity (B, panels c and d). Numbers on the left in panel B (panels a and b) are molecular masses in kilodaltons. Lanes M, markers.