Plays a role in the inhibition of host apoptosis to facilitate efficient viral replication. Promotes stabilization and inactivation of host TP53 through interaction with host MDM2. Interacts with host MDM2; this interaction leads to the stabilization of host TP53. localized in the host nucleus at early times postinfection and then increases in both nuclear and cytoplasmic compartments during the course of infection. Belongs to the beta-herpesvirinae UL38 protein family. Extended N-terminus.