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 (By similarity). Induces host mTORC1 activation by antagonizing the ability of host TSC1/2 to negatively regulate mTORC1. Thus, inhibits a growth regulatory pathway to facilitate viral replication. Prevents premature cell host cell death by blocking host ubiquitin-specific protease 24/USP24-mediated autophagic ferritin degradation in lysosomes thus maintaining lysosome integrity and cellular viability (PubMed:29695420). Interacts with host MDM2; this interaction leads to the stabilization of host TP53 (By similarity). Interacts with host TSC2; this interaction prevents host cell stress responses. Interacts with host USP24. 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.