A high phosphorylation state and increased activity of the TRE motif in the NIH3T3 cell transformant induced by retTPC.

A 57 kDa protein was detected in an NIH3T3 transformant induced by retTPC, an activated form of the ret proto-oncogene which encodes a receptor-tyrosine kinase. A high phosphorylation state and increased activity of a TPA responsive element was observed in the transformant. Increased expression of c-jun mRNA was also detected. A 40 kDa protein in the retTPC transformant, which was specifically immunoprecipitable with v-jun antiserum, was highly phosphorylated mainly at a serine residue(s). These data suggest that an aberrant signal triggered by a retTPC product affects the cellular serine/threonine phosphorylation state resulting in high phosphorylation of c-jun protein.