EQUINE HERPESVIRUS-1 GENE-12, THE FUNCTIONAL HOMOLOG OF HERPES-SIMPLEX VIRUS VP16, TRANSACTIVATES VIA OCTAMER SEQUENCES IN THE EQUINE HERPESVIRUS IE GENE PROMOTER

The HSV-1 transactivator of immediate-early (IE) gene expression, VP16 , has several functional homologues among the alphaherpesviruses which have not yet been extensively studied in relation to their modes of a ction. To date, nothing is known of the exact sites or mechanism of in teraction of the equine herpesvirus type 1 (EHV-1) homologue, the gene 12 protein, with the EHV-1 IE promoter. We show that the gene 12 prot ein utilises the promoter proximal region of the IE gene to induce act ivation and identify four potential octamer DNA binding sites within t hat region. Although there was divergence from its consensus, Oct-1 bo und to each of these sites in an in vitro complex formation assay, and in the presence of the gene 12 product a second complex of slower mig ration, which was also dependent on Oct-1, was detected. When each sit e was inserted into a basal promoter, two conferred activation by gene 12 with a resulting increase in expression of up to 50-fold compared to basal levels. These results show that, despite the differences betw een the two proteins, the mechanism of interaction of the gene 12 prot ein with its target is analogous to that of VP16. (C) 1995 Academic Pr ess, Inc.