Ribosomal protein S6 kinase II <p>This entry represents ribosomal protein S6 kinase II [<cite idref="PUB00042703"/>]. This enzyme acts as a serine/threonine kinase required for the mitogen or stress-induced phosphorylation of the transcription factors CREB (cAMP response element-binding protein) and ATF1 (activating transcription factor-1). It plays an essential role in the control of RELA transcriptional activity in response to TNF. It directly represses transcription via phosphorylation of Ser-1 of histone H2A. It phosphorylates Ser-10 of histone H3 in response to mitogenics, stress stimuli and epidemal growth-factor (EGF), which results in the transcriptional activation of several immediate early genes, including proto-oncogenes c-fos/FOS and c-jun/JUN. It mediates the mitogen- and stress-induced phosphorylation of high mobility group protein 14 (HMG-14). It requires magnesium ions as a cofactor.</p>