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Updated: Jun 27, 2026

Temporal Analysis of the Nuclear-to-cytoplasmic Translocation of a Herpes Simplex Virus 1 Protein by Immunofluorescent Confocal Microscopy
06:40

Temporal Analysis of the Nuclear-to-cytoplasmic Translocation of a Herpes Simplex Virus 1 Protein by Immunofluorescent Confocal Microscopy

Published on: November 4, 2018

Nuclear import of HSV-1 DNA polymerase processivity factor UL42 is mediated by a C-terminally located bipartite

Gualtiero Alvisi1, Simone Avanzi, Daniele Musiani

  • 1Dipartimento di Ematologia e Scienze Oncologiche L.A. Seragnoli, Universita degli Studi di Bologna, Bologna, Italia. gualtiero.alvisi3@unibo.it

Biochemistry
|December 5, 2008
PubMed

Insights

The human herpes simplex virus type 1 (HSV-1) DNA polymerase accessory protein UL42 is imported into the nucleus via a bipartite nuclear localization signal. Inhibiting both UL42 and UL30 nuclear localization signals may block HSV-1 replication.

Area of Science:

  • Virology
  • Molecular Biology
  • Cell Biology

Background:

  • The human herpes simplex virus type 1 (HSV-1) DNA polymerase accessory protein UL42 is crucial for viral replication.
  • UL42 enhances the processivity of the catalytic subunit UL30.

Purpose of the Study:

  • To investigate the nuclear import mechanism of HSV-1 UL42.
  • To explore the role of UL42's nuclear localization signal (NLS) in viral replication.
  • To assess the potential of targeting NLSs for antiviral strategies.

Main Methods:

  • Studied UL42 nuclear import in living cells using Ran- and energy-dependent assays.
  • Utilized mutant UL42 derivatives lacking the bipartite NLS (UL42-NLSbip).
  • Examined nuclear translocation of the HSV-1 DNA polymerase holoenzyme (UL42 and UL30) upon infection or coexpression.
  • Investigated the function of individual NLS components and their impact on nuclear transport.

Main Results:

  • UL42 is imported into the nucleus via a C-terminal bipartite NLS (UL42-NLSbip) in a Ran- and energy-dependent manner.
  • Cytoplasmic UL42 mutants relocalize to the nucleus upon HSV-1 infection or UL30 coexpression, suggesting cytoplasmic holoenzyme assembly.
  • Simultaneous mutation of UL42 and UL30 NLSs retains the holoenzyme in the cytoplasm, inhibiting viral replication.
  • Individual NLS components (NLSA and NLSB) are insufficient for nuclear targeting alone, indicating a requirement for cooperative function.
  • Substitution of specific residues (P or G) in the NLS with alanine partially restores nuclear import function.

Conclusions:

  • The HSV-1 DNA polymerase holoenzyme can assemble in the cytoplasm before nuclear translocation.
  • Targeting both UL42 and UL30 NLSs presents a potential strategy to inhibit HSV-1 replication.
  • The findings redefine the consensus for monopartite NLSs, highlighting the importance of adjacent basic residues and specific amino acid compatibility (e.g., P/G at position +3).

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