Regulation of Protein Synthesis in Frog Virus 3-Infected Cells

Abstract

One of the first consequences of frog virus 3 (FV3) interaction with the host cell is a marked inhibiton of cellular protein synthesis. One or several proteins present in the virus particles are responsible for the observed inhibition, which results in the initiation step of cellular message translation being impaired.

Viral proteins are sequentially synthesized and coordinately regulated. They are classified into three major groups on the basis of their temporal synthesis. The first group comprising mRNAs is translated in the presence of residual host protein synthesis. Production of the second group of viral proteins is accompanied by a complete shut off of cellular translation. The last group of proteins is synthesized as a result of selective translation of late gene transcripts since several transcription products of immediate early or early genes, although present, are not translated late in infection. Two observations may be related to the translational discrimination between the transcripts of early and late genes. Virus-induced or modified factors are produced and are required for efficient translation of late viral mRNA. The 5′ leader of some late transcripts of immediate early genes shows additional sequences when compared to the corresponding immediate early transcripts, suggesting that these sequences could impair translation. Thus both transcriptional and translational regulation are combined to control FV3 gene expression.