The abundance of the herpes simplex virus type 1 UL37 tegument protein in virus particles is closely controlled.

The tegument region of herpes simplex virus type 1 virus particles contains approximately 15 virus-encoded polypeptide species. One of the less abundant species is a 120 kDa protein specified by gene UL37. The abundance of the UL37 protein in infected cells was increased about 20-fold by replacing the native promoter for gene UL37 with the strong immediate early promoter of human cytomegalovirus. This rise in abundance did not induce any detectable increase in the amount of UL37 protein incorporated into virus particles. These data contrast with those previously obtained for a second tegument protein VP22 whose level of incorporation was elevated by increasing its abundance in infected cells. Thus, for the UL37 protein, a mechanism exists to control its abundance in the tegument. Moreover, data obtained with light particles which lack the viral capsid suggest that this controlled incorporation is not directed by interaction with the capsid structure.