BiP binding keeps ATF6 at bay.

A study by, in this issue of Developmental Cell shows that transport to the Golgi complex and subsequent proteolytic activation of the stress-regulated transcription factor ATF6 is initiated by the dissociation of the ER chaperone BiP from ATF6. This demonstrates that BiP is a key element in sensing the folding capacity within the ER and provides mechanistic insights on how the activation of membrane-bound transcription factors can be regulated.