Translational control of viral gene expression in eukaryotes

As obligate intracellular parasites, viruses rely exclusively on the transl ational machinery of the host cell for the synthesis of viral proteins. Thi s relationship has imposed numerous challenges on both the infecting virus and the host cell. Importantly, viruses must compete with the endogenous tr anscripts of the host cell for the translation of viral mRNA. Eukaryotic vi ruses have thus evolved diverse mechanisms to ensure translational efficien cy of viral mRNA above and beyond that of cellular mRNA. Mechanisms that fa cilitate the efficient and selective translation of viral mRNA may be inher ent in the structure of the viral nucleic acid itself and can involve the r ecruitment and/or modification of specific host factors. These processes se rve to redirect the translation apparatus to favor viral transcripts and th ey often come at the expense of the host cell. Accordingly, eukaryotic cell s have developed antiviral countermeasures to target the translational mach inery and disrupt protein synthesis during the course of virus infection. N ot to be outdone many viruses have answered these countermeasures with thei r own mechanisms to disrupt cellular antiviral pathways, thereby ensuring t he uncompromised translation of virion proteins Here we review the varied a nd complex translational programs employed by eukaryotic viruses. We discus s how these translational strategies have been incorporated into the virus life cycle and examine how such programming contributes to the pathogenesis of the host cell.