RT Journal Article SR Electronic(1) A1 Caselmann, Wolfgang H A1 Renner, Matthias A1 Schlüter, Volker A1 Hofschneider, Peter Hans A1 Koshy, Rajen A1 Meyer, MarkusYR 1997 T1 The hepatitis B virus MHBst167 protein is a pleiotropic transactivator mediating its effect via ubiquitous cellular transcription factors JF Journal of General Virology, VO 78 IS 6 SP 1487 OP 1495 DO https://doi.org/10.1099/0022-1317-78-6-1487 PB Microbiology Society, SN 1465-2099, AB C-terminally truncated surface proteins of hepatitis B virus (HBV) are frequently translated from genomically integrated viral sequences. They may be relevant for hepatocarcinogenesis by stimulating gene expression. First, we examined the transactivating potential of middle hepatitis B surface protein truncated at amino acid (aa) position 167 (MHBst167) on the HBV regulatory element. In transient cotransfection assays using Chang liver or HepG2 cell lines and chloramphenicol acetyl- transferase (CAT) reporter constructs only the HBV enhancer I, but no other HBV regulatory elements like the X promoter, the S1 or S2 promoter or the enhancer II/core promoter could be stimulated by MHBst167. Since there is no evidence for a direct interaction of MHBst167 with DNA, we subsequently analysed whether cellular transcription factors were involved in mediating transactivation. This was tested both with isolated transcription-factor-binding sites and in the natural context of viral and cellular promoter elements. Deletion analysis and electrophoretic mobility shift assays revealed that Sp1,AP1 and NF-kB can mediate transactivation by MHBst167. No involvement of CREB, NF1 or the liver- specific factor C/EBP was found. These data indicate that MHBst167 is a pleiotropic, non-liver-specific transactivator which exerts its effect via ubiquitous cellular transcription factors that are also involved in the regulation of expression of cellular genes relevant for proliferation and inflammation., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-78-6-1487