The hepatitis B virus large surface protein (LHBs) is a transcriptional activator

It has been shown that a C-terminally truncated form of the middle-sized hepatitis B virus (HBV) surface protein (MHBs(t)) functions as a transcriptional activator. This function is dependent on the cytosolic orientation of the N-terminal PreS2 domain of MHBs(t), but in the case of wild-type MHBs, the PreS2 domain is cotranslationally translocated into the ER lumen. Recent reports demonstrated that the PreS2 domain of the large HBV surface protein (LHBs) initially remains on the cytosolic side of the ER membrane after translation. Therefore, the question arose as to whether the LHBs protein exhibits the same transcriptional activator function as MHBs(t). We show that LHBs, like MHBs(t), is indeed able to activate a variety of promoter elements. There is evidence for a PKC-dependent activation of AP-1 and NF-kappa B by LHBs. Downstream of the PKC the functionality of c-Raf-1 kinase is a prerequisite for LHBs-dependent activation of AP-1 and NF-kappa B since inhibition of c-Raf-1 kinase abolishes LHBs-dependent transcriptional activation of AP-1 and NF-kappa B. (C) 1996 Academic Press, Inc.