The herpes simplex virus type 1 (HSV-1) UL31 and UL34 proteins are dependent on each other for proper targeting to the nuclear membrane and are required for efficient envelopment of nucleocapsids at the inner nuclear membrane. The UL31 protein localized diffusely throughout the nucleus in infected Vero cells and the distribution patterns of the UL31 protein appeared to be different from those of either replication protein ICP8 or capsid protein ICP35. Additionally, fluorescence results showed that the predicted nuclear export signal (NES) might be nonfunctional, and the functional NES of UL31 might require a specific conformation. Here we focus on transport inside epithelial cells of newly synthesized virus during its transit to the cell surface. Like other herpesviruses, herpes simplex virus 1 (HSV-1) has evolved a vesicle-mediated nucleocytoplasmic transport mechanism for nuclear egress of nascent progeny nucleocapsids. Still another polyclonal antibody indicated virtually no difference in lamin A/C staining in infected versus uninfected cells, indicating that the HSV-induced changes are more conformational than the result of lamin depletion at the nuclear rim. However, unlike the wild-type virus, the mutant virus failed to enter into the axoplasm of ganglionic neurons.
The effects on very early events in expression are surprising in light of the fact that U(L)31 is designated a late gene and pU(L)31 is not a virion component. We show herein that while most pUL31 is expressed late in infection, low levels of pU(L)31 are detectable as early as 2 h postinfection, consistent with an early role in HSV-1 infection.