Reduced Polyomavirus DNA replication as a consequence of a late-region deletion that results in early mRNA instability

The ionophore monensin inhibits mouse polyomavirus DNA replication and destabilizes viral early mRNAs

Monensin is a ionophore compound with different biological activities. It raises the intralysosomal pH, it binds the plasma membranes particularly at the level of the cisternal system of the Golgi apparatus. It causes imbalance in the intramembrane ion traffic and inhibits export of secretory proteins at membrane level. Monensin blocks endocytosis and therefore impedes entry of toxic molecules. The drug also inhibits viral proliferation of RNA and DNA viruses such as vesicular stomatitis, influenza and human polyomaviruses. In this report we show that monensin effectively abolishes viral DNA replication of mouse polyomavirus. Results show that the half life of viral early mRNAs is significantly reduced in the presence of the drug. Therefore we suggest that the reduction of viral DNA synthesis is a consequence of the reduced intranuclear pool of viral early antigens.

Mouse polyomavirus late region mutants expressing a defective VP2 capsid protein exhibit an enhanced viral DNA replication

We have constructed mouse polyomavirus mutants with deletions or insertions in the late region. These viral constructs exhibit two different phenotypes, characterized by a differential replication ability. The first type shows a twofold higher level of DNA synthesis with respect to wild type, while mutants of the second type are virtually unable to replicate. In this paper we investigate the replicative behavior of the first class of mutants, which expresses defective viral coat proteins. Our data raise the possibility that, of the three late gene viral products, VP2 is involved in the formation of an encapsidation intermediate that, in an indirect fashion, affects the rate of viral DNA synthesis.