Mitogen- and stress-activated kinase 1 (MSK1; EC 2.7.11.1) and MSK2 are nuclear protein kinases that regulate transcription downstream of the ERK1/2 (extracellular-signal-regulated kinase 1/2) and p38α MAPKs (mitogen-activated protein kinases) via the phosphorylation of CREB (cAMP-response-element-binding protein), ATF1, and histone H3. MSKs are most closely related to the RSK family of kinases and, similar to RSK, they contain two kinase domains in a single polypeptide. Mice lacking MSK1 or MSK2, and also a double knockout of both MSK1 and MSK2, are viable and fertile, but show enhanced inflammation in immune models as well as impairments in some models of memory[1].