Abstract
The HSV gene encoding ICP4 is negatively regulated and the HSV gene encoding thymidine kinase is positively regulated by ICP4 in vivo. We report that ICP4 is a component of a stable complex that contains protein and a sequence of approximately 28 nucleotides that span the ICP4 gene transcription initiation site. The association of ICP4 with DNA sequences between positions -103 and +32 relative to the ICP4 mRNA start site was demonstrated by DNA binding immunoassays. DNase footprinting revealed that nucleotides between positions -8 and +20 are protected by ICP4. In contrast, binding of ICP4 to sequences flanking the mRNA start site in the thymidine kinase gene was not observed. Models for ICP4-mediated positive or negative regulation of HSV gene transcription are discussed.