mitogen activated protein kinases. (ERKs: externally regulated kinases) serine threonine kinases that are activated when quiescent cells are treated with mitogens and therefore potentially transmit signal for entry into cell cycle. One target is trancription factor p62TCF. Map kinase itself can be phosphorylated by map kinase kinase and this may in turn be controlled by RAF 1. Confusingly, do phosphorylate microtubule-associated proteins.