Activation of members of the mitogen-activated protein kinase family is a major mechanism for transduction of extracellular signals. Stress-activated protein kinases are one subclass of MAP kinases. The protein encoded by this gene functions as a signal transducer during differentiation of myoblasts to myotubes.By screening with sequences based on those of the rat ERK3 gene, Lechner et al. (1996) isolated an ERK6 clone from a human skeletal muscle cDNA library. They reported that ERK6 appears to function as a signal transducer during differentiation of myoblasts to myotubes. Li et al. (1996) stated that SAPK3 is probably identical to the ERK6 gene cloned by Lechner et al. (1996).