Final answer:
Once ATF6 reaches the Golgi, it undergoes B) cleavage and activation to become the active form of the transcription factor involved in the unfolded protein response (UPR) pathway.
Step-by-step explanation:
Once ATF6 reaches the Golgi, it undergoes cleavage and activation. ATF6 is a transcription factor involved in the unfolded protein response (UPR) pathway, which is activated when there is an accumulation of misfolded proteins in the endoplasmic reticulum (ER).
During the UPR, ATF6 is transported from the ER to the Golgi apparatus. In the Golgi, ATF6 is cleaved by proteases, resulting in the release of its active form.
The active form of ATF6 then translocates to the nucleus, where it binds to specific DNA sequences and activates the expression of genes involved in protein folding and ER stress response.
Therefore, the correct answer is B) Cleavage and activation.