Expression and nuclear envelope localization of biologically active fusion glycoprotein gB of herpes simplex virus in mammalian cells using cloned DNA.

Herpes simplex virus (HSV) is known to bud from the inner membrane of the nuclear envelope. The structural gene for the glycoprotein gB, which is essential for virus entry and cell fusion induced by HSV type 1, has been cloned in a transient expression vector containing the adenovirus major late promoter, tripartite leader sequence, and VARNA (a special RNA in adenovirus-infected cells) genes. Synthesis and glycosylation of glycoprotein gB was observed in COS-1 cells transfected with the vector containing the gB gene. Removal of a 3' fragment of the cloned gene resulted in the synthesis and secretion of a truncated gB glycoprotein. Immunofluorescence studies revealed that the expressed glycoprotein was localized in the nuclear envelope as well as in the cell surface. The expressed gB-1 glycoprotein was biologically active and induced fusion of cells to produce polykaryons. These data show that HSV glycoprotein gB expressed from cloned gene can be used as a model to study targeting of proteins into the nuclear envelope as well as cell fusion induced by the virus.