Beet yellows virus replicase and replicative compartments: parallels with other RNA viruses

Vladimir A Gushchin,Alexey A Agranovsky,Tatyana N Erokhina,Andrey G Solovyev,Sergey Y Morozov

doi:10.3389/fmicb.2013.00038

Abstract

In eukaryotic virus systems, infection leads to induction of membranous compartments in which replication occurs. Virus-encoded subunits of the replication complex mediate its interaction with membranes. As replication platforms, RNA viruses use the cytoplasmic surfaces of different membrane compartments, e.g., endoplasmic reticulum (ER), Golgi, endo/lysosomes, mitochondria, chloroplasts, and peroxisomes. Closterovirus infections are accompanied by formation of multivesicular complexes from cell membranes of ER or mitochondrial origin. So far the mechanisms for vesicles formation have been obscure. In the replication-associated 1a polyprotein of Beet yellows virus (BYV) and other closteroviruses, the region between the methyltransferase and helicase domains (1a central region (CR), 1a CR) is marginally conserved. Computer-assisted analysis predicts several putative membrane-binding domains in the BYV 1a CR. Transient expression of a hydrophobic segment (referred to here as CR-2) of the BYV 1a in Nicotiana benthamiana led to reorganization of the ER and formation of ~1-μm mobile globules. We propose that the CR-2 may be involved in the formation of multivesicular complexes in BYV-infected cells. This provides analogy with membrane-associated proteins mediating the build-up of “virus factories” in cells infected with diverse positive-strand RNA viruses (alpha-like viruses, picorna-like viruses, flaviviruses, and nidoviruses) and negative-strand RNA viruses (bunyaviruses).

Highlights

Eukaryotic viruses from disparate groups, both DNA and RNA containing ones, induce in cells drastic rearrangement of the membranes leading to formation of “virus organelles” or “virus factories”
The tubes are in close contact with mitochondria and rough endoplasmic reticulum (ER), possibly serving as sources of host factors aiding the virus replication
The replicative complexes consisting of Bunyamwera virus (BunV) nucleoproteins and RNA replicase, concentrate on the inner surface of the globular domain

Summary

Introduction

Eukaryotic viruses from disparate groups, both DNA and RNA containing ones, induce in cells drastic rearrangement of the membranes leading to formation of “virus organelles” or “virus factories”. The BunV replication-associated globular domains are open structures, unlike the vesicles and spherules induced by positive-sense RNA viruses (see below). 5 -open reading frames (ORFs) 1a and 1b, and translation of the genomic RNA yields polyproteins 1a and 1ab autocatalytically processed into non-structural proteins forming the replication complex (reviewed in Gorbalenya, 2008).

Results

Conclusion