Proteasome-dependent, ubiquitin-independent degradation of Daxx by the viral pp71 protein in human cytomegalovirus-infected cells

The cellular Daxx protein represses human cytomegalovirus (HCMV) gene expression from the major immediate early promoter. HCMV prevents Daxx-mediated silencing during lytic infection by delivering the viral pp71 tegument protein to the nucleus, where pp71 binds to and induces the proteasomal degradation of Daxx. In this study, we show that a functional ubiquitin pathway is not required for the proteasomal degradation of the endogenous Daxx protein by tegument-delivered pp71 in HCMV-infected cells, demonstrating that the pp71-mediated degradation of Daxx occurs through a proteasome-dependent, ubiquitin-independent pathway.