Virus–host interactions: insights from the replication cycle of the large Paramecium bursaria chlorella virus

• Published in: Cellular microbiology Vol. 18; no. 1; pp. 3 - 16
• Main Authors: Milrot, Elad, Mutsafi, Yael, Fridmann‐Sirkis, Yael, Shimoni, Eyal, Rechav, Katya, Gurnon, James R., Van Etten, James L., Minsky, Abraham
• Format: Journal Article
• Language: English
• Published: England Hindawi Limited 01.01.2016
• Subjects: Animals; Chlorella virus; Genomes; Host-Pathogen Interactions; Humans; Macromolecular Substances - ultrastructure; Mice; Mimiviridae - physiology; Optical Imaging; Paramecium - virology; Paramecium bursaria; Paramecium bursaria chlorella virus 1; Phycodnaviridae - growth & development; Phycodnaviridae - physiology; Vaccinia virus - physiology; Virus Replication
• ISSN: 1462-5814; 1462-5822
• DOI: 10.1111/cmi.12486

Summary The increasing interest in cytoplasmic factories generated by eukaryotic‐infecting viruses stems from the realization that these highly ordered assemblies may contribute fundamental novel insights to the functional significance of order in cellular biology. Here, we report the formation process and structural features of the cytoplasmic factories of the large dsDNA virus Paramecium bursaria chlorella virus 1 (PBCV‐1). By combining diverse imaging techniques, including scanning transmission electron microscopy tomography and focused ion beam technologies, we show that the architecture and mode of formation of PBCV‐1 factories are significantly different from those generated by their evolutionary relatives Vaccinia and Mimivirus. Specifically, PBCV‐1 factories consist of a network of single membrane bilayers acting as capsid templates in the central region, and viral genomes spread throughout the host cytoplasm but excluded from the membrane‐containing sites. In sharp contrast, factories generated by Mimivirus have viral genomes in their core, with membrane biogenesis region located at their periphery. Yet, all viral factories appear to share structural features that are essential for their function. In addition, our studies support the notion that PBCV‐1 infection, which was recently reported to result in significant pathological outcomes in humans and mice, proceeds through a bacteriophage‐like infection pathway. By using cutting‐edge imaging techniques the elaborate structure of the replication factory generated by the giant dsDNA Paramecium bursaria chlorella virus 1 (PBCV‐1) in host cells was resolved. PBCV‐1 factory consists of a network of membrane bilayers acting as capsid templates in the central region, and viral genomes spread throughout the host cytoplasm. These studies highlight the fact that whereas cytoplasmic factories produced by different viruses are profoundly diverse, they all share structural features that are essential for their function.