INHIBITION OF 80 KDA PROTEIN-PHOSPHORYLATION BY SHORT-WAVELENGTH UV-LIGHT IN NIH 3T3 CELLS

The exposure of NIH 3T3 fibroblast cells to 254 nm UV radiation result ed in a temporary depression of DNA synthesis and inhibition of 80 kDa protein phosphorylation. This inhibition of protein phosphorylation w as correlated with decreased protein kinase C activity in the membrane fractions of UV-damaged cells. The inositol triphosphate contents mea sured, by the competitive binding assay using bovine adrenal binding p rotein, showed 80% reduction in the fibroblasts treated with 15 J/m2 o f UV light. The intracellular diacylglycerol concentration was also ma rkedly reduced in UV-damaged cells. The results suggest that UV light causes acute reductions of inositol triphosphate and diacylglycerol co ntents in cells along with decreases in membrane protein kinase C acti vity, which leads to the inhibition of phosphorylation of an acidic pr otein of 80 kDa.