The Ubiquitin Ligase Itch and Ubiquitination Regulate BFRF1-mediated Nuclear Envelope Modification for EBV Maturation

摘要

The cellular endosomal sorting complex required for transport (ESCRT) was recently found to mediate important morphogenesis processes at the nuclear envelope (NE). We previously showed that the Epstein-Barr virus (EBV) BFRF1 protein recruits the ESCRT-associated protein Alix to modulate NE structure and promote EBV nuclear egress. Here, we uncover new cellular factors and mechanisms involved in this process. BFRF1-induced NE vesicles are similar to those observed following EBV reactivation. BFRF1 is ubiquitinated and elimination of possible ubiquitination with either lysine mutations or fusion of a de-ubiquitinase hampers NE-derived vesicle formation and virus maturation. While interacting with multiple Nedd4-like ubiquitin ligases, BFRF1 binds Itch ligase preferably. We show that Itch associates with Alix and BFRF1, and is required for BFRF1-induced NE vesicle formation. Our data demonstrate that Itch, ubiquitin and Alix control the BFRF1-mediated modulation of the NE and EBV maturation, uncovering novel regulatory mechanisms of nuclear egress of viral nucleocapsids.