Description
MSK1 or mitogen- and stress-activated protein kinase-1 contains 2 protein kinase domains and shares 43% protein sequence identity with the MAPKAPK1 isoforms. Northern blot analysis shows that MSK1 is expressed in all tissues with the highest level of expression in brain, muscle, and placenta. Immunoelectron microscopy localized MSK1 to the nucleus. MSK1 is activated in vitro and in vivo by either ERK or SAPK2 proteins. MSK1 rather than MAPKAP-K1 or MAPKAP-K2/K3, mediates activation of the cAMP response element-binding protein and activating transcription factor-1 by either growth factors or stress signals. By radiation hybrid analysis, the RPS6KA5 gene has been mapped to chromosome 14q31-q32