Partial complementation between the immediate early proteins ICP4 of herpes simplex virus type 1 and IE180 of pseudorabies virus.

We previously described that the immediate early (IE) IE180 protein of PRV can down-regulate the transactivation of the ICP4 promoter of HSV-1, and that the d120 virus (an ICP4-deficient HSV-1 strain) can partially replicate its viral DNA in the presence of the IE180 protein. Herein, we demonstrate that this partial complementation of d120 by IE180 is sufficient for transcription of β, γ1 and γ2 products such as DNA pol, VP16 and gC, respectively. However, expression levels are low for VP16 and even lower for the gC, such that IE180 is unable to fully substitute for ICP4 functionally. Viral progeny was not detected in PK15 cells expressing PRV IE180.