Transformation by ras oncogene induces nuclear shift of protein kinase C

We measured protein kinase C (PKC) activity in normal and ras-transformed Balb/3T3 fibroblasts; cytosolic and nuclear-associated PKC activity was determined either as phorbol ester binding, PKC-dependent phosphorylation of histone III-S, or phosphorylation of endogenous nuclear proteins. Results demonstrate that ras-transformed fibroblasts show down-regulation of cytosolic PKC accompanied by increase of nuclear-associated PKC. These results provide evidence linking transformation to PKC nuclear shift with consequent phosphorylation of nuclear proteins.