A model of a hydroxyurea-induced SAR1-mediated pathway for activating transcription in erythroid cells. Hydroxyurea binds to an unknown cellular receptor, leading to ATM-mediated activation of NF-κB, which in turn activates transcription of the SAR1 promoter, possibly facilitated by cobinding of Elk-1 or EKLF. Increased SAR1 activates JNK/Jun in association with the G protein Giα, affecting the cell cycle and enhancing γ-globin expression. Some of the moderators have yet to be identified. Professional illustration by Patrick Lane, ScEYEnce Studios.