The C terminus of the herpes simplex virus UL25 protein is required for release of viral genomes from capsids bound to nuclear pores

Jamie B. Huffman, Gina R. Daniel, Erik Falck-Pedersen, Alexis Huet, Greg A. Smith, James F. Conway, Fred L. Homa*

*Corresponding author for this work

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The herpes simplex virus (HSV) capsid is released into the cytoplasm after fusion of viral and host membranes, whereupon dynein-dependent trafficking along microtubules targets it to the nuclear envelope. Binding of the capsid to the nuclear pore complex (NPC) is mediated by the capsid protein pUL25 and the capsidtethered tegument protein pUL36. Temperature-sensitive mutants in both pUL25 and pUL36 dock at the NPC but fail to release DNA. The uncoating reaction has been difficult to study due to the rapid release of the genome once the capsid interacts with the nuclear pore. In this study, we describe the isolation and characterization of a truncation mutant of pUL25. Live-cell imaging and immunofluorescence studies demonstrated that the mutant was not impaired in penetration of the host cell or in trafficking of the capsid to the nuclear membrane. However, expression of viral proteins was absent or significantly delayed in cells infected with the pUL25 mutant virus. Transmission electron microscopy revealed capsids accumulated at nuclear pores that retained the viral genome for at least 4 h postinfection. In addition, cryoelectron microscopy (cryo-EM) reconstructions of virion capsids did not detect any obvious differences in the location or structural organization for the pUL25 or pUL36 proteins on the pUL25 mutant capsids. Further, in contrast to wild-type virus, the antiviral response mediated by the viral DNA-sensing cyclic guanine adenine synthase (cGAS) was severely compromised for the pUL25 mutant. These results demonstrate that the pUL25 capsid protein has a critical role in releasing viral DNA from NPC-bound capsids.

Original languageEnglish (US)
Article numbere00641-17
JournalJournal of virology
Volume91
Issue number15
DOIs
StatePublished - Aug 1 2017

Keywords

  • CVSC
  • Cryo-electron microscopy
  • Genome uncoating
  • HSV-1
  • Nuclear pores
  • PUL25

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Insect Science
  • Virology

Fingerprint Dive into the research topics of 'The C terminus of the herpes simplex virus UL25 protein is required for release of viral genomes from capsids bound to nuclear pores'. Together they form a unique fingerprint.

  • Cite this