Pyrrolidine dithiocarbamate prevents p53 activation and promotes p53 cysteine residue oxidation.

Pyrrolidine dithiocarbamate (PDTC) is a thiol compound widely used to study the activation of redox-sensitive transcription factors. Although normally used as an antioxidant, PDTC has been shown to exert pro-oxidant activity on proteins both in vitro and in vivo. Because p53 redox status has been shown to alter its DNA binding capability, we decided to test the effect of PDTC on p53 activation. In this communication, we report that PDTC inhibits the activation of temperature-sensitive murine p53(Val-135) (TSp53) in the transformed rat embryo fibroblast line, A1-5, as well as wild-type human p53 in the normal diploid fibroblast line, WS1neo. In A1-5 cells, PDTC abrogated UV- and temperature shift-induced TSp53 nuclear translocation and p53-mediated transactivation of MDM2. PDTC also blocked UV-induced accumulation of wild-type p53 in WS1neo cells. Continual presence of PDTC was required for its effect as both UV-induced nuclear translocation and accumulation resumed after PDTC removal. We next investigated whether PDTC treatment altered the p53 redox state. We found that PDTC increased p53 cysteine residue oxidation in vivo. This represents the first direct evidence showing that the p53 redox state can be altered in vivo and that increased oxidation correlates with its inability to perform its downstream functions.