14-3-3-PROTEINS BIND TO HISTONE AND AFFECT BOTH HISTONE PHOSPHORYLATION AND DEPHOSPHORYLATION

14-3-3 proteins appear to play a critical role in Ca2+-stimulated secretion in permeabilized chromaffin cells. 14-3-3 proteins have been reported to be both stimulators and inhibitors of protein kinase C (PKC). We have found that 14-3-3 proteins, isolated on the basis of their ability to enhance secretory activity, stimulated histone phosphorylation by PKC, but they had no effect on myosin light chain phosphorylation by PKC. 14-3-3 proteins were also found to inhibit the rate of [P-32]histone dephosphorylation but not the rate of [P-32]myosin light chain dephosphorylation. Cross-linking experiments and affinity chromatography demonstrated that 14-3-3 proteins bind to histones. These results suggest that at least some of the reported effects of 14-3-3 proteins on PKC activity may result from 14-3-3 proteins binding to histone.