Ultrastructural localization of the herpes simplex virus type 1 UL31, UL34, and US3 proteins suggests specific roles in primary envelopment and egress of nucleocapsids

The wild-type U(L)31, U(L)34, and U(S)3 proteins localized on nuclear membranes and perinuclear virions; the U(S)3 protein was also on cytoplasmic membranes and extranuclear virions. The UL31 and UL34 proteins were not detected in extracellular virions. U,3 deletion caused (i) virion accumulation in nuclear membrane invaginations, (ii) delayed virus production onset, and (iii) reduced peak virus titers. These data support the herpes simplex virus type 1 deenvelopment-reenvelopment model of virion egress and suggest that the U(S)3 protein plays an important, but nonessential, role in the egress pathway.