NUCLEAR-LOCALIZATION AND TRANSCRIPTIONAL ACTIVATION ACTIVITIES OF TRUNCATED VERSIONS OF THE IMMEDIATE-EARLY GENE-PRODUCT OF EQUINE HERPESVIRUS-1

The equine herpesvirus 1 (EHV-1) immediate-early (IE) gene product enc odes a nuclear regulatory protein capable of negatively autoregulating its own promoter, transactivating representative EHV-1 early promoter s, and acting in a concerted fashion with accessory EHV-1 regulatory f actors to transactivate EHV-1 late promoters. To identify IE amino aci d sequences involved in nuclear localization and to examine the contri bution of C-terminal portions of the IE polypeptide to transactivation , vectors that express various carboxy-terminally truncated IE polypep tides were constructed. It is demonstrated that amino acids 963 throug h 970 of the 1,487-amino-acid IE protein are required for efficient lo calization of the truncated IE polypeptides to the nuclei of transfect ed cells. In addition, it is demonstrated that the first 970 amino aci ds of the IE gene product are sufficient to transactivate the EHV-1 th ymidine kinase promoter to significant levels (i.e., approximately 40% of the level of wild-type activation).