1. Department of Sciences, University of Basilicata, 85100 Potenza, Italy;2. Department of Biochemistry and Biophysics, Stockholm University, 106 91 Stockholm, Sweden;3. CNR Institute of Biomembranes and Bioenergetics, 70125 Bari, Italy
Abstract:
Hepatitis B x antigen up-regulates the liver expression of URG7 that contributes to sustain chronic virus infection and to increase the risk for hepatocellular carcinoma by its anti-apoptotic activity. We have investigated the subcellular localization of URG7 expressed in HepG2 cells and determined its membrane topology by glycosylation mapping in vitro. The results demonstrate that URG7 is N-glycosylated and located to the endoplasmic reticulum membrane with an Nlumen–Ccytosol orientation. The results imply that the anti-apoptotic effect of URG7 could arise from the C-terminal cytosolic tail binding a pro-apoptotic signaling factor and retaining it to the endoplasmic reticulum membrane.