Replication and Expression Strategies of Viruses

Regardless of their genetic constitution, viral genomes are replicated, expressed, and assembled in association with living host cells. These entities do not undergo division, but rather generate new particles through the assembly of preformed components. Some viruses go further by modifying cellular metabolism to create a more favorable environment for viral gene expression. In a few instances, these clever strategies also facilitate escape from the host’s defense responses. The process of replication is typically divided into the phases of attachment, entry, uncoating, genome replication and expression, assembly, maturation, and finally, egress or release from the host cell. In this chapter, we address genome replication and expression, including the multiple strategies that serve to control gene expression and ensure preferential propagation of the virus.