Adenovirus VAI-RNA regulates gene expression by controlling stability of ribosome-bound RNAs

Adenovirus VAI-RNA is a small virally encoded RNA that is required for efficient protein synthesis at late times of adenoviral infection. We show that in transient transfection assays VAI-RNA promotes not only an increased level of protein encoded by a co-transfected marker (CAT) plasmid, but also a marked accumulation of its transcript. The increases in CAT protein and RNA levels reflect an enhanced stability of the cytoplasmic RNA as shown by primer extension analyses of RNA isolated from transfected cells upon transcriptional arrest. Surprisingly, the ability of VAI to activate expression of CAT requires the translation of a substantial portion of the RNA: when translation is prevented by elimination of the initiator AUG codon or by introduction of stop codons 5' to codon 107, VAI-RNA is no longer capable of increasing CAT RNA levels; the introduction of stop codons 3' of codon-135, on the other hand, does not significantly impair VAI-RNA function. We conclude that in addition to its role as a specific activator of translation, adenovirus VA genes function to regulate the stability of ribosome-bound RNA.