The complexity of the mammalian p53 pathway and protein kinase C (PKC) family has hampered the discrimination of the effect of PKC isoforms on p53 activity. Using yeasts co-expressing the human wild-type p53 and a mammalian PKC-alpha, -delta, -epsilon or -zeta, we showed a differential regulation of p53 activity and phosphorylation state by PKC isoforms. Whereas PKC-alpha reduced the p53-induced yeast growth inhibition and cell cycle arrest, PKC-delta and -epsilon enhanced the p53 activity through p53 phosphorylation, and PKC-zeta had no effect on p53. This work identified positive and negative p53 regulators which represent promising pharmacological targets in anti-cancer therapy.