FIG. 3.

HCV replicons activate ATF6. (A) Structure of ATF6. ATF6 is an ER transmembrane protein. Upon ER stress, the cytoplasmic N-terminal domain of ATF6 is cleaved at the cytoplasmic face of the ER membrane. The cleaved cytoplasmic domain is translocated to the nucleus where it activates the transcription of ER chaperone genes containing the ERSE. TM is the region of the protein that spans the ER membrane. The ATF6 cleavage sites are indicated by arrows (45). (B) HCV replicons induce the cleavage of endogenous p90ATF6 to p50ATF6. Total and nuclear Huh7 and FCA4 cell lysates were immunoprecipitated with anti-ATF6 antibody. Molecular masses (in kilodaltons) are indicated at left.