FIG. 1.

Inhibition of p53-dependent transactivation by anti-p53 antibodies. p53 transactivation activity was stimulated in early-passage LacZ21 fibroblasts either by irradiation with 10 of UV J · m⁻² (A to C) or by microinjection of the activating antibody PAb421 (D to F). Expression of the p53-dependent reporter was assessed 24 h later by β-gal histochemistry (punctate and/or diffuse blue staining). Microinjected cells were identified by immunoperoxidase detection of injected IgG (brown staining). Injection of either DO-1 (B) or PAb1801 (C) 24 h prior to UV treatment greatly reduced reporter expression compared to that with mouse IgG controls (A). Similarly, the response to PAb421 (D) was inhibited by coinjection of DO-1 (E) or PAb1801 (F). (Note that the β-gal-positive [blue] cells in panels B and C [arrows] were not microinjected.) Magnification, ×140.