Final answer:
The cytosolic part of ATF6 binds to ER stress sensors, such as IRE1, to regulate the expression of genes involved in ER homeostasis and the unfolded protein response (UPR). Option C is correct.
Step-by-step explanation:
The cytosolic part of ATF6 binds to ER stress sensors. ATF6 is a transcription factor that is involved in the unfolded protein response (UPR), which is activated in response to endoplasmic reticulum (ER) stress. When ER stress is detected, ATF6 translocates to the Golgi apparatus, where it is cleaved to release its cytosolic domain.
This cytosolic part of ATF6 then binds to ER stress sensors, such as IRE1 and PERK, to regulate the expression of genes involved in ER homeostasis and the UPR.