The protein ATF6 is a constitutively expressed transcription factor that is a key mediator of the unfolded protein response (UPR) that allows mammalian cells to maintain cellular homeostasis under conditions of environmental and physiological stress. ATF6 is endoplasmic reticulum (ER) membrane-anchored in its inactive form, and under certain stress conditions, translocates to the Golgi where it is processed into its active form through action of the S1P and S2P proteases.
