9zm2
Human cytomegalovirus UL52 4-mer
Structural highlights
FunctionUL52_HCMVA Plays a role in efficient localization of neo-synthesized capsids to nuclear replication compartments, thereby controlling cleavage and packaging of virus genomic DNA.[1] Publication Abstract from PubMedTo create a new wave of infectious virions, all herpesviruses require an accessory factor of unknown function to package their viral genomes into nascent capsids. Here, we present cryo-EM structures of the packaging accessory factor from the alpha-herpesvirus herpes simplex virus type 1 (HSV-1, UL32) and the beta-herpesvirus human cytomegalovirus (HCMV, UL52). Unlike homologs from the gamma-herpesviruses, neither UL32 nor UL52 form stable homopentameric rings. UL52 forms incomplete pentameric rings lacking one or two protomers. UL32 does not form stable higher-order species, but stabilization through chemical crosslinking revealed a novel quaternary structure where three pentameric rings assemble into a "tripentamer." Our results reveal that herpesvirus packaging accessory factors adopt distinct oligomeric states but are constrained to pentameric symmetry. Assembly of protomers into a ring creates a positively charged central channel that we show is critical for infectious virus production in HSV-1. Taken together, our study points to a structurally conserved, essential function of packaging accessory factors across the Herpesviridae. Conserved assembly architecture of the essential herpesvirus packaging accessory factor.,Bailey EJ, Devarkar SC, Szczepaniak R, Meissner LM, Chen X, Wu C, Weller SK, Xiong Y, Didychuk AL bioRxiv [Preprint]. 2026 Jan 22:2026.01.22.701024. doi: , 10.64898/2026.01.22.701024. PMID:41648366[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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