Properties and Function of JNK1 c-Jun N-terminal kinase 1 (JNK1), also commonly known as Mitogen-Activated Protein Kinase 8 (MAPK8), is a member of the JNK subgroup of MAP kinases. JNK1 is encoded by the MAPK8 gene. MAP kinases form a superfamily of protein kinases that function by phosphorylating various protein substrates, including transcription factors, which