A cis-acting element within the 5′ leader of a cytomegalovirus β transcript determines kinetic class

Abstract

During cytomegalovirus (CMV) infection, gene expression is regulated by transcriptional and posttranscriptional events. Although recent studies have established that posttranscriptional controls are important determinants of gene expression in several eukaryotic systems, the precise signals and mechanisms have not been clearly identified. We present evidence for a cis-acting signal, contained within the 5′ leader region of a CMV β (or early) gene, that acts posttranscriptionally in the regulation of gene expression. Addition of this signal to an α (or immediate early) gene construct converted expression of the indicator protein to the β class, even though the gene remained under α transcriptional control. Deletion of a portion of the β gene leader sequence (nucleotides +62 to +142) reverted expression to the α class. This cis-dominant signal appers to act by blocking expression posttranscriptionally until a viral function activates full gene expression at the appropriate time in infection.