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Updated: Jun 25, 2026
MicroRNA-based Regulation of Picornavirus Tropism
Published on: February 6, 2017
Murine Polyomavirus encodes a microRNA that cleaves early RNA transcripts but is not essential for experimental
Christopher S Sullivan1, Chang K Sung, Christopher D Pack
1The University of Texas at Austin, Institute for Cellular and Molecular Biology, Section of Molecular Genetics and Microbiology, 1 University Station A5000, Austin TX 78712-0162, USA. chris_sullivan@mail.utexas.edu
Abstract:
MicroRNAs are small regulatory RNAs that post-transcriptionally regulate gene expression and can be encoded by viral as well as cellular genomes. The functions of most viral miRNAs are unknown and few have been studied in an in vivo context. Here we show that the murine polyomavirus (PyV) encodes a precursor microRNA that is processed into two mature microRNAs, both of which are active at directing the cleavage of the early PyV mRNAs. Furthermore, we identify a deletion mutant of polyomavirus that is defective in encoding the microRNAs. This mutant replicates normally and transforms cultured cells with efficiencies comparable to wildtype PyV. The miRNA mutant is competent to establish a transient infection of mice following parenteral inoculation, and is cleared post infection at approximately the same rate as the wildtype virus. In addition, under these laboratory conditions, we observe no differences in anti-viral CD8 T cell responses. These results indicate that PyV miRNA expression is not essential for infection of cultured cells or experimentally inoculated mice, and raise the possibility that its role in natural infection might involve aspects of acquisition or spread that are not recapitulated by experimental inoculation.
Insights
Murine polyomavirus (PyV) microRNAs are not essential for viral replication or infection in cell cultures or mice. Their role in natural infection may involve spread or acquisition, not tested in this study.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- MicroRNAs (miRNAs) are small regulatory RNAs influencing gene expression.
- Viral miRNAs, including those from murine polyomavirus (PyV), have largely unknown functions.
- Few viral miRNAs have been studied in an in vivo context.
Purpose of the Study:
- To investigate the role of PyV-encoded microRNAs in viral infection and host response.
- To characterize a PyV mutant lacking miRNA expression.
Main Methods:
- Identification and characterization of a PyV deletion mutant lacking miRNA genes.
- Assessment of viral replication and cell transformation efficiencies in vitro.
- Evaluation of PyV infection, viral clearance, and CD8 T cell responses in experimentally inoculated mice.
Main Results:
- PyV encodes a precursor miRNA processed into two mature, active miRNAs that cleave viral mRNAs.
- A PyV deletion mutant lacking miRNAs replicates normally and transforms cells comparably to wildtype.
- The miRNA mutant establishes transient infections in mice and is cleared similarly to wildtype, with no observed differences in CD8 T cell responses.
Conclusions:
- PyV miRNA expression is not essential for infection of cultured cells or experimentally inoculated mice.
- The function of PyV miRNAs in natural infection may relate to viral acquisition or spread, which are not fully recapitulated in experimental models.
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