text: Three of the many proteins that are phosphorylated by MAPK are shown in the figure to the right. One effect of MAPK activation is to alter the translation of mRNA to proteins. MAPK phosphorylates the 40S ribosomal protein S6 kinase (RSK). This activates RSK, which, in turn, phosphorylates ribosomal protein S6. Mitogen-activated protein kinases that phosphorylate ribosomal protein S6 were the first to be isolated.
  MAPK regulates the activities of several transcription factors. MAPK can phosphorylate C-myc. MAPK phosphorylates and activates MNK, which, in turn, phosphorylates CREB. MAPK also regulates the transcription of the C-Fos gene. By altering the levels and activities of transcription factors, MAPK leads to altered transcription of genes that are important for the cell cycle.
  The 22q11, 1q42, and 19p13 genes, by affecting the ERK pathway, are associated with schizophrenia, schizoaffective disorder, bipolar disorder, and migraines.