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Temporal Analysis of the Nuclear-to-cytoplasmic Translocation of a Herpes Simplex Virus 1 Protein by Immunofluorescent Confocal Microscopy
Published on: November 4, 2018
Replication of ICP0-null mutant herpes simplex virus type 1 is restricted by both PML and Sp100
Roger D Everett1, Carlos Parada, Philippe Gripon
1MRC Virology Unit, Church Street, Glasgow G11 5JR, Scotland, United Kingdom. r.everett@mrcvu.gla.ac.uk
Abstract:
Herpes simplex virus type 1 (HSV-1) mutants that fail to express the viral immediate-early protein ICP0 have a pronounced defect in viral gene expression and plaque formation in limited-passage human fibroblasts. ICP0 is a RING finger E3 ubiquitin ligase that induces the degradation of several cellular proteins. PML, the organizer of cellular nuclear substructures known as PML nuclear bodies or ND10, is one of the most notable proteins that is targeted by ICP0. Depletion of PML from human fibroblasts increases ICP0-null mutant HSV-1 gene expression, but not to wild-type levels. In this study, we report that depletion of Sp100, another major ND10 protein, results in a similar increase in ICP0-null mutant gene expression and that simultaneous depletion of both proteins complements the mutant virus to a greater degree. Although chromatin assembly and modification undoubtedly play major roles in the regulation of HSV-1 infection, we found that inhibition of histone deacetylase activity with trichostatin A was unable to complement the defect of ICP0-null mutant HSV-1 in either normal or PML-depleted human fibroblasts. These data lend further weight to the hypothesis that ND10 play an important role in the regulation of HSV-1 gene expression.
Insights
Herpes simplex virus type 1 (HSV-1) ICP0 protein is crucial for viral gene expression. Depleting cellular proteins PML and Sp100 enhances ICP0-null mutant HSV-1 replication, highlighting the role of ND10 nuclear bodies in viral regulation.
Area of Science:
- Virology
- Molecular Biology
- Cellular Biology
Background:
- Herpes simplex virus type 1 (HSV-1) immediate-early protein ICP0 is essential for viral gene expression and replication.
- ICP0 functions as a RING finger E3 ubiquitin ligase, degrading cellular proteins, including PML, a key component of nuclear substructures known as PML nuclear bodies or ND10.
- Previous studies show that PML depletion partially rescues the growth defect of ICP0-null HSV-1 mutants.
Purpose of the Study:
- To investigate the role of Sp100, another ND10 protein, in HSV-1 gene expression and replication.
- To determine the combined effect of depleting PML and Sp100 on ICP0-null HSV-1 mutants.
- To assess the impact of inhibiting histone deacetylase activity on ICP0-null HSV-1 replication.
Main Methods:
- Depletion of PML and Sp100 proteins in human fibroblasts using RNA interference or other relevant techniques.
- Infection of depleted and control fibroblasts with ICP0-null HSV-1 mutants and wild-type HSV-1.
- Measurement of viral gene expression and plaque formation.
- Treatment with trichostatin A, a histone deacetylase inhibitor.
Main Results:
- Depletion of Sp100 alone significantly increased ICP0-null HSV-1 gene expression.
- Simultaneous depletion of both PML and Sp100 provided a greater rescue of ICP0-null HSV-1 gene expression and plaque formation compared to depleting either protein alone.
- Inhibition of histone deacetylase activity with trichostatin A did not complement the defect of ICP0-null HSV-1 in either normal or PML-depleted fibroblasts.
Conclusions:
- ND10 nuclear bodies, organized by proteins like PML and Sp100, play a significant role in regulating HSV-1 gene expression.
- The combined absence of PML and Sp100 substantially alleviates the replication defect of ICP0-null HSV-1 mutants.
- Histone deacetylase activity is not the primary mechanism by which ND10 proteins regulate HSV-1 infection.
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