IDENTIFICATION AND ZINC DEPENDENCE OF THE BOVINE HERPESVIRUS-1 TRANSACTIVATOR PROTEIN BICPO

Bovine herpesvirus 1 (BHV-1) specifies an unspliced early 2.6-kb RNA ( ER2.6) which is 3' coterminal,vith exon 2 of the 2.9-kb immediate-earl y (IE) RNA. The two transcripts have a common open reading frame (676 codons). The predicted protein, designated BHV-1 infected cell protein 0 (BICP0), contains a zinc finger domain with homology to ICP0 of her pes simplex virus type 1 and protein 61 of varicella-zoster virus, and depending on the promoter, it acts as a strong activator or as a repr essor in transient expression assays. In situ immunoadsorbent assays u sing antisera against synthetic oligopeptides demonstrated that BICP0 accumulates in nuclei of BHV-1-infected cells, as expected for an IE g ene product involved in gene regulation. Western blots (immunoblots) r evealed a BHV-1-specific 97-kDa protein which was detectable during th e IE phase and also at later periods of infection, indicating that the kinetics of BICP0 synthesis is consistent with the switch from IER2.9 to ER2.6. To confirm that ER2.6 encoded the 97-kDa BICP0 protein, a D NA fragment containing BICP0-coding sequences was inserted into the Au tographa californica baculovirus genome. A recombinant protein, identi fied by its reactivity,vith antipeptide sera, exhibited the same elect rophoretic mobility as BICP0 specified by BHV-1. We microinjected Xeno pus oocytes with a BICP0 effector plasmid and a promoter-chloramphenic ol acetyltransferase plasmid. BICP0-induced stimulation of this promot er was strongly reduced when intracellular zinc was chelated by thione in, indicating that the effect of BICP0 is zinc dependent.