Varicella-zoster virus (VZV) gene 62 encodes a protein with a predicted of 140000 (140K) which has considerable amino acid identity with the major immediate early (IE) protein Vmw175 (ICP4) of herpes simplex virus type 1 (HSV-1). Vmw175 is an essential virus polypeptide with a pivotal role in the activation of early and late viral gene expression and also in the repression of IE gene expression. The VZV 140K protein has been shown to function as a strong transcriptional activator in transfection assays and largely complements for the loss of Vmw175 function in HSV-1. We report the results of cotransfection experiments which demonstrate that the 140K protein strongly represses expression from its own promoter, that of gene 62, thus establishing further functional similarity between it and Vmw175. However, whereas Vmw175 can substitute for the 140K protein in repression of the gene 62 promoter, the 140K protein does not repress the HSV-1 IE3 promoter in the reciprocal experiment. The integrity of a domain of Vmw175 (designated region 2), previously shown to be crucial for repression of the HSV-1 IE3 promoter, is also required for repression of the gene 62 promoter. Moreover, a similar requirement for the highly similar region 2 of the 140K protein for repression is demonstrated, suggesting that VZV 140K protein and HSV-1 Vmw175 autoregulate IE gene expression by a related mechanism.


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