MSK1 also known as RLPK, RPS6KA5 is a key player in the mitogen-activated protein kinase (MAPK) signaling cascade, which is essential for various cellular processes, including cell growth, differentiation, and response to stress. MSK1 phosphorylates histone H3 and other substrates, thereby influencing gene expression and chromatin remodeling. This post-translational modification regulates transcriptional responses to extracellular signals, making MSK1 an important target for understanding cancer biology and other diseases linked to aberrant signaling pathways. MSK1 shares structural similarities with other ribosomal S6 kinase family members, which mediate cellular responses to growth factors and stress signals, highlighting MSK1′s importance in cellular homeostasis and signaling.