XPO1 coordinates human cytomegalovirus maturation by modulating genome encapsidation and secondary envelopment

Human cytomegalovirus (HCMV) replication depends on tightly coordinated nuclear capsid assembly and cytoplasmic nucleocapsid maturation, yet host factors controlling these processes remain poorly defined. Here, we identify exportin 1 (XPO1) as a dual-phase regulator that coordinates HCMV maturation from nucleus to cytoplasm. XPO1 inhibition induces aberrant nuclear electron-dense speckles and accumulation of B-capsids. Mechanistically, nuclear retention of pp65 drives speckle formation but does not account for B-capsid accumulation. XPO1 recognizes a functional nuclear export signal (NES) within pUL77 and regulates its proper intranuclear localization. Inhibiting XPO1 or disrupting the NES induces intranuclear pUL77 aggregation and B-capsid accumulation. XPO1 is also required for viral assembly compartment formation and maintenance of late-stage autophagic flux, both of which are essential for secondary envelopment. Our findings highlight the key role of XPO1 in virion maturation and the therapeutic potential of repurposing FDA-approved XPO1 inhibitors as a host-directed antiviral strategy.