regulation of ultraviolet binduced phosphorylation of histone h3 at serine 10 by fyn kinase ultraviolet b uvb induces phosphorylation of histone h3 at serine 10 and mitogenactivated protein kinases are involved in this signal transduction pathway here we provide evidence that fyn kinase a member of the src kinase family is involved in the uvbinduced phosphorylation of histone h3 at serine 10 uvb distinctly increased fyn kinase activity and phosphorylation fyn kinase inhibitors 4amino54chlorophenyl7tbutylpyrazol34dpyramide and leflunomide an src kinase inhibitor suppressed both uvbinduced phosphorylation of histone h3 at serine 10 and fyn kinase activity and phosphorylation uvbinduced phosphorylation of histone h3 at serine 10 was blocked by either a dominantnegative mutant of fyn dnmfyn kinase or small interfering rna of fyn kinase uvbinduced phosphorylation and activities of erks and protein kinase bakt were markedly inhibited by dnmfyn kinase however dnmfyn kinase did not inhibit uvbinduced phosphorylation of p38 mapk or cjun nterminal kinases active fyn kinase phosphorylated histone h3 at serine 10 in vitro and the phosphorylated fyn kinase could translocate into the nucleus of hacat cells these results indicate that fyn kinase plays a key role in the uvbinduced phosphorylation of histone h3 at serine 10