Both Vps4A and CHMP1A are localized in the vicinity of viral cytoplasmic assembly compartments, sites of viral maturation that develop in CMV-infected cells. Localization of CHMP1A and Vps4A proteins in the vicinity of AC, where the final steps in virus maturation and envelopment occur, indicates an important role of ESCRT pathway during these processes in HCMV life cycle. Both Vps4A and CHMP1A, the ESCRT-III component, influence the outcome of ESCRT recruitment via upstream parallel pathways using Tsg101, ALIX, or HECT-Ub ligases. Vps4A contributes to all three known primary mechanisms of ESCRT recruitment by viruses. Tsg101, a component of ESCRT-I, normally functions to deliver ubiquitinated transmembrane proteins to MVBs. ALIX binds to Tsg101 in addition to ESCRT-III protein CHMP-4B, thus linking ESCRT-I and ESCRT-III.
VPS4A and CHMP1A components localize within the assembly compartment (AC), with a striking colocalization of the chromatin modifying protein 1A (CHMP1A) and assembled gM:gN. Both the Vps4A and CHMP1A localized in the vicinity of viral cytoplasmic assembly compartments are sites of viral maturation that develop in human cytomeglovirus (HCMV)-infected cells. The accumulation of viral tegument also occurs during this step of viral maturation.