MSK-1 is a mitogen and stress activated protein kinase-1 which belongs to the AGC family of kinases and is related in structure to the ribosomal p70 S6 kinase subfamily. MSK-1can be activated by ERK1/2 and SAPK2 /p38 MAP kinase. It is also known to be required for the phosphorylation of CREB, ATF1 H3 and HMG-14 in response to mitogen and stress. Similar to RSK, MSK-1 contains two kinase domains (N-term and a C-term). Once phosphorylated on Thr581 and Ser360 by ERK1/2 and SAPK2/p38, MSK-1 autophosphorylate on at least 5 sites. Of these autophosphorylation sites Ser212 and Ser376 get phosphorylated by the C-terminal kinase domain of MSK-1 which is essential for the catalytic activity of the N-terminal kinase domain.