Identification of transactivator and nuclear localization domains in the Epstein-Barr virus DNA polymerase accessory protein, BMRF1

The Epstein-Barr virus (EBV) BMRF1 gene product is an essential component o f the viral DNA polymerase and is absolutely required for lytic virus repli cation. In addition to its polymerase accessory protein function, we recent ly demonstrated that BMRF1 is a transactivator, inducing expression of the essential oriLyt promoter, BHLF1. However, the regions of BMRF1 required fo r transactivation of BHLF1 are unknown. Here we demonstrate that the carbox y-terminal portion of the BMRF1 protein (amino acids 378-404), although not required for DNA binding or polymerase processivity function, is required for transactivator function as well as nuclear localization. Site-directed mutagenesis of this region allowed us to separate the transactivator and nu clear localization motifs of BMRF1. The two DNA-binding domains of BMRF1 ar e also required for efficient transactivation of the BHLF1 promoter.