33 Reovirus Translational Control

Abstract

THE REOVIRIDAE FAMILY
Reoviridae are cytolytic parasites that infect a broad spectrum of insect, plant, and vertebrate species, including humans (Nibert et al. 1996). They can readily initiate replication because they contain, as virally encoded components, all the enzymes necessary to produce functional viral mRNAs. However, like other viruses, Reoviridae require the host translational machinery to complete the replicative cycle, and control mechanisms operate in infected cells to facilitate a shift from cellular to viral protein synthesis. Several regulatory events have been suggested to explain how this is accomplished, but even the intensively studied continued translation of reoviral mRNAs in the face of initiation shutoff by the interferon-induced, double-stranded (ds) RNA-activated protein kinase (PKR; see Chapters 8 and 13) remains incompletely understood and controversial.

The prototype dsRNA-containing reoviruses were isolated from mammals including humans and characterized in the 1950s and 1960s (Fields 1996). Later discoveries of other dsRNA viruses from mammals, fish, birds, insects, plants, and diverse organisms including fungi and bacteria demonstrated that viruses with segmented dsRNA genomes are widely distributed and successfully established in nature. The Reoviridae family of metazoan dsRNA viruses has been divided into nine genera based on host range and a genome segment number between 10 and 12. They include the Orthoreoviruses (10), Orbiviruses (10), Rotaviruses (11), and Coltiviruses (12) which all replicate in humans; the Phytoviruses (12), Oryzaviruses (10), and Fijiviruses (10) of plants; Aquareoviruses (11) of fish and shellfish; and Cypoviruses (10) that grow in insects.

In addition to the common features of...