Related Experiment Video
Updated: May 4, 2026
Measurement of γHV68 Infection in Mice
Published on: November 22, 2011
Murine gammaherpesvirus 68 encodes a second PML-modifying protein
Jaturong Sewatanon1, Paul D Ling
1Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.
Abstract:
The ORF75c tegument protein of murine gammaherpesvirus 68 (MHV68) promotes the degradation of the antiviral promyelocytic leukemia (PML) protein. Surprisingly, MHV68 expressing a degradation-deficient ORF75c replicated in cell culture and in mice similar to the wild-type virus. However, in cells infected with this mutant virus, PML formed novel track-like structures that are induced by ORF61, the viral ribonucleotide reductase large subunit. These findings may explain why ORF75c mutant viruses unable to degrade PML had no demonstrable phenotype after infection.
Insights
Murine gammaherpesvirus 68's ORF75c protein usually degrades the PML protein. However, a mutant virus unable to degrade PML showed similar replication, suggesting ORF61 induces alternative PML structures.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Murine gammaherpesvirus 68 (MHV68) is a model gammaherpesvirus.
- The ORF75c protein is a tegument protein of MHV68.
- The promyelocytic leukemia (PML) protein has antiviral functions.
Purpose of the Study:
- To investigate the role of ORF75c in PML degradation.
- To determine the in vivo and in vitro phenotype of MHV68 lacking ORF75c's PML degradation function.
- To understand the interplay between ORF75c, PML, and ORF61 during MHV68 infection.
Main Methods:
- Generation of MHV68 expressing a degradation-deficient ORF75c mutant.
- Viral replication assays in cell culture.
- In vivo replication studies in mice.
- Immunofluorescence microscopy to visualize PML structures.
Main Results:
- MHV68 with degradation-deficient ORF75c replicated similarly to wild-type MHV68 in cell culture and mice.
- In cells infected with the mutant virus, PML formed novel track-like structures.
- These PML structures were induced by ORF61, the viral ribonucleotide reductase large subunit.
Conclusions:
- ORF75c's role in PML degradation is not essential for MHV68 replication in vitro or in vivo.
- ORF61 can induce alternative PML structures, potentially compensating for the lack of ORF75c-mediated degradation.
- These findings explain the lack of a demonstrable phenotype in ORF75c mutant viruses unable to degrade PML.
