JUN and skin neoplasm: A mutant allele of c-Jun, in which the JNK phosphoacceptor Ser63 and Ser73 are changed to alanines (JunAA), reduced both oncogenic transformation caused by constitutive activation of the Ras pathway in immortalized fibroblasts and skin tumor development (22), indicating a protumorigenic role of c-Jun N-terminal phosphorylation in Ras-induced transformation.