Control of expression of the varicella-zoster virus major immediate early gene

The cis-acting DNA sequences and trans-acting proteins that control the expression of the major immediate early (IE) gene of varicella-zoster virus (VZV) were investigated. The location of the IE mRNA 5' terminus was determined by primer extension and S1 nuclease analyses and the functional activities of DNA sequences upstream of this site were analysed by a transfection assay. The VZV IE promoter exhibited low activity in BHK and HeLa cells, but was transactivated by the herpes simplex virus type 1 (HSV-1) virion protein Vmw65. DNA sequences between positions -131 and +57 were responsible for promoter activity, whereas sequences between -410 and -131 mediated the response to Vmw65. Two short elements in the -410 to -131 region formed protein-DNA complexes with HeLa cell nuclear proteins and formed a ternary complex when Vmw65 was added. One of the elements, ATGTAAATGAAAT, possessed a strong similarity to the HSV-1 TAATGARAT. The VZV homologue of Vmw65, encoded by open reading frame (ORF) 10, failed to trans-activate expression from HSV-1 or VZV IE promoters and did not form a ternary complex with functional TAATGARAT elements and HeLa cell proteins. Therefore, stimulation of VZV IE transcription by Vmw65 can occur by a mechanism similar to that employed by HSV-1, but VZV ORF 10 does not function as a trans-activator of IE gene expression.