The unique architecture of Bunyamwera virus factories around the Golgi complex

Abstract

SummaryViral factories are novel structures built by viruses in infected cells. During their construction organelles are recruited and build a large scaffold for viral replication and morphogenesis. We have studied how a bunyavirus uses the Golgi to build the factory. With the help of confocal and 3D ultrastructural imaging together with molecular mapping in situ and in vitro we have characterized a tubular structure that harbours the viral replication complexes in a globular domain. Numerous ribonucleoproteins were released from purified tubes disrupted in vitro. Actin and myosin I were identified by peptide mass fingerprinting in isolated tubes while actin and the viral NSm non-structural protein were detected in the tubes' internal proteinaceous scaffold by immunogold labelling. Studies with NSm deletion mutants and drugs affecting actin showed that both NSm and actin are key factors for tube and virus assembly in Golgi. Three-dimensional reconstructions based on oriented serial sections of infected cells showed that tubes anchor cell organelles to Golgi stacks and make contacts with intracellular viruses. We propose that this new structure, unique among enveloped viruses, assembles in association with the most stable component of Golgi stacks, the actincontaining matrix scaffold, connecting viral replication and morphogenesis inside viral factories.

Arenavirus Infection Induces Discrete Cytosolic Structures for RNA Replication

“…1) and are not polyadenylated (23). Based on a growing body of work describing the cytoplasmic life cycles of a number of RNA viruses (14,21,22,25,26,38), arenavirus replication is likely to be compartmentalized to specialized virus-induced organelles referred to as replication-transcription complexes (RTCs).As a starting point for understanding the viral and cellular requirements for arenavirus replication, we have determined the intracellular localization and composition of RTCs generated during infection by the attenuated vaccine strain of JUNV (Candid#1) (31) and a closely related nonpathogenic species, Tacaribe virus (TCRV). We find that viral RNA synthesis takes place in discrete cytosolic puncta whose formation is induced in part by the virus nucleoprotein (N).…”

A unique virus release mechanism in the Archaea

“…In such cases, the structures of the factory are enclosed by a membrane to exclude cellular organelles. Ribosomes are, however, present, and the factory is dedicated to viral genome replication and virion assembly (24,25). The eukaryotic viral factories were suggested to constitute the genuine identity of viruses (26), which thus might be considered as a specific type of living organisms (26,27).…”

Schmallenberg virus: continuing a trend?

“…1,40 Bunyaviruses replicate in the cytoplasm of infected cells and assemble in the lumen of Golgi stacks. [41][42][43][44][45] The viral glycoproteins, Gn and Gc, and the nonstructural protein, NSm, are encoded by the mRNA segment. Gn and Gc form a heterodimer that is retained in the Golgi to allow virus assembly.…”