EXPRESSION OF CALMODULIN AND CALMODULIN-BINDING PROTEINS IN RAT FIBROBLASTS STABLY TRANSFECTED WITH PROTEIN-KINASE-C AND ONCOGENES

Molecular mechanisms leading to elevated calmodulin (CaM) expression i n cancer have not yet been discovered. We have quantitated the levels of transcripts derived from all three CaM genes in a variety of the sa me origin rat fibroblasts transformed with oncogenes in combination wi th gene for protein kinase C using Northern blot analysis with three C aM gene specific cDNA probes. Five species of CaM mRNA were detected i n all these cells. Surprisingly many of the investigated cell lines ex hibited a decreased content of all CaM mRNAs as compared to control ce lls with CaMI and CaMII transcripts showing the most pronounced altera tions. In contrast, CaM protein levels were increased in all these cel l lines as determined by a radioimmunoassay. These results suggest tha t oncogenic up-regulation of CaM synthesis takes place posttranscripti onally. Several CaM binding proteins were found at different concentra tions in the studied cell lines depending on the oncogenes used for tr ansformation. However, CaM overexpression does not seem to affect the overall levels of CaM binding proteins. (C) 1997 Elsevier Science B.V.