MAPK8(Mitogen-activated protein kinase 8) is also named as JNK1,PRKM8,SAPK1,SAPK1C and belongs to the MAP kinase subfamily. MAPK8 is activated by dual phosphorylation at a Thr-Pro-Tyr motif during response to UV light. MAPK8 functions to phosphorylate c-Jun at N-terminal serine regulatory sites of Ser-63 and Ser-73,mapping within the transactivation domain. Phosphorylation of these sites in response to UV results in transcriptional activation of c-Jun. It has 4 isoforms produced by alternative splicing with the molecular weight of 46 kDa and 48 kDa. This protein can be phosphorylated and this antibody recognizes the 46 kDa and 55 kDa bands in western blot.