The Kinetics of Protein Synthesis in Pseudorabies Virus
Abstract
Pseudorabies virus (PrV) is a member of the herpesvirus
family and is molecularly similar to herpes simplex virus (HSV).
The glycosalated proteins as well as the non-glycosalated
proteins of PrV are thought to be temporally regulated in a
cascade pattern similar to that described for HSV-I. Proteins are classified as α, β, β8, and 8 proteins based on their kinetics and requirements for synthesis.
PrV gX, a major PrV glycoprotein, was characterized as a PrV β
protein, based on the kinetics of protein synthesis in 5 virus
strains.
The kinetics of gX synthesis were studied in the parent
strain, PrV HR, when gX synthesis is directed by its own promoter
sequence. gp50 synthesis was studied in the recombinant virus
PrV x50, when gp50 synthesis is directed by the gX promoter
sequence. tPA synthesis was also studied in the recombinant
virus PrV tPA, when tPA synthesis is directed by the gX promoter
sequence. tPA or tissue plasminogen activator, a model gene was
inserted downstream from the gX promoter sequence to examine PrV
as a vector for foreign gene expression. gX in PrV HR, gp50 in
PrV x50, and tPA in PrV tPA all were expressed as early as 2
hours postinfection, suggesting that gX is a PrV β protein.
The data also suggests that some inherent difference in the
stability of the mRNA in the infected cell could explain the
appearance of gX throughout infection and the disappearance of
both gp50 and tPA by 8 hours of infection, when regulated by the
gX promoter sequence.
The kinetics of gX synthesis were also studied in the
recombinant viruses HSVgX and HSVSgX. gX synthesis in HSVgX,
when gX synthesis is regulated by its own promoter sequence,
strongly resembles gX synthesis in PrV HR. This supports the
classification of gX as a PrV β protein. gX synthesis in
HSVSgX, when gX is regulated by the ICPS (major capsid protein)
promoter sequence, strongly resembles HSV ICPS synthesis,
suggesting that gX synthesis is strongly influenced by the HSV
ICPS β8 promoter sequence.