ENHANCED P53 ACTIVITY AND ACCUMULATION IN RESPONSE TO DNA-DAMAGE UPONDNA TRANSFECTION

In response to DNA damage the wild-type tumor suppressor protein p53 a ccumulates in the nucleus of rodent and primate cells. To investigate the minimal requirement for this reaction the cellular DNA was restric ted by two alternative ways: (i) by calicheamicin gamma 1, an enediyne , which causes direct, sequence-specific DNA damage, as shown by fluor imetric analysis of DNA unwinding and by poly(ADP-ribose) polymerase a ctivation. The dose-dependent DNA damage correlated with the nuclear p 53 accumulation. In addition, restriction was generated (ii) by the in tracellular introduction of the restriction enzyme PvuII, which genera tes blunt-ended DNA breaks, applying a mild hypotonic shock (pellet me thod). Previous transfection of linear or circular, single- or ds, DNA , followed by mitomycin C-treatment, lead to a dramatic increase in nu clear p53 accumulation and p53 activity according to electrophoretic m obility shift analysis. The nature of transfected DNA was irrelevant f or enhanced accumulation. The data suggest, that the cellular p53 resp onse to DNA damage is sensitized by uptake of exogenous DNA.