RNA Regulatory Elements in the Genomes of Simple Retroviruses

Abstract

The RNA genomes of simple retroviruses encode three genes (gag, pol,andenv) which are required for replication. In addition, there are at least three well-definedcis-acting structures which regulate important aspects of the viral life cycle. The packaging signal at the 5′ end of the RNA tags the genomic RNA for specific encapsidation into assembling virus. Since viral Env proteins are translated from spliced mRNAs,cis-acting splicing signals ensure that the proper ratio of spliced and unspliced viral RNAs is present in the infected cell. Finally,cis-acting elements at the 3′ end of the genome promote the export of unspliced RNAs from the nucleus for translation and encapsidation.