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

Abstract

The tegument region of herpes simplex virus type 1 virus particles contains approximately 15 virusencoded 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.

Differential protein partitioning within the herpesvirus tegument and envelope underlies a complex and variable virion architecture

“…On the high end, the pUS3 and pUL46 tegument proteins had CV approximating unfused GFP indicating there was no copy control of these proteins despite, at least in the case of pUL46, a high average copy number. The low CV of pUL36 and pUL37 was equivalent to the copy-controlled acquisition of capsid protein pUL25, and was consistent with findings of an immunoblot study of pUL37 incorporation (35). These findings indicated a degree of flexibility in virion assembly that varied among the tegument proteins.…”

Tyrosine Phosphorylation of Bovine Herpesvirus 1 Tegument Protein VP22 Correlates with the Incorporation of VP22 into Virions

“…The abundance of VP22 in HSV-1 virions can be regulated by the VP22 expression levels in the infected cells (21). In contrast, incorporation of HSV-1 tegument protein UL37 into the virions is tightly controlled (25).…”

“…This observation is consistent with the hypothesis that the incorporation of tegument protein is partly determined by local protein concentration. In contrast, the amount of HSV-1 tegument protein UL37 in virions is strictly controlled despite a 20-fold increase of UL37 in infected cells (25). Thus, multiple mechanisms to control the incorporation of different tegument proteins may exist.…”

“…In addition, the loss of VP22 tyrosine phosphorylation correlated with reduced incorporation of VP22 compared to that of envelope glycoprotein D in the mutant viruses but not with the amount of VP22 produced during virus infection. Our data suggest that tyrosine phosphorylation of VP22 plays a role in virion assembly.The tegument is a unique feature of herpesviruses and remains the least well-characterized virion compartment (41).There are approximately 15 virally encoded proteins that participate in the assembly of the amorphous tegument structure, and these tegument proteins occupy the majority of the mass in the virion (18,25,40). Recent studies have shown that at least a portion of the tegument structure has an ordered organization and interacts with the capsid (37,42,43,47,48); however, little is known regarding the acquisition of the viral tegument process (14,15,36,38,41).…”

“…There are approximately 15 virally encoded proteins that participate in the assembly of the amorphous tegument structure, and these tegument proteins occupy the majority of the mass in the virion (18,25,40). Recent studies have shown that at least a portion of the tegument structure has an ordered organization and interacts with the capsid (37,42,43,47,48); however, little is known regarding the acquisition of the viral tegument process (14,15,36,38,41).…”