Expression regulation of major late promoter tripartite leader sequence in adenovirus late infection

OBJECTIVE: To investigate the influence of adenovirus major late tripartite leader sequence on specific exportation of virus mRNA in the late phase of adenovirus infection. METHODS: We constructed a marked, human beta-actin minigene under the control of the glucocorticoid-inducible enhancer and promoter of mouse mammary tumor virus, and inserted it into the left end of the adenovirus type V genome. The promoter gene, designated MA, as well as of a sibling, which differed only in inclusion of a cDNA copy of the adenovirus major late tripartite leader sequence upstream of beta-actin sequences termed MtplA, in recombinant virus-infected cells was strictly dependent on addition of deoxymethesone to the medium. Nuclear and cytoplasmic reporter RNA species were compared by Northern blotting, primer extension and pulse-chase assay. RESULTS: The high concentrations of newly-synthesized RNA were accumulated in cytoplasm when tripartite leader sequence was present in reporter RNA, despite the equal rates of transcription of the two reporter genes. Nuclear and cytoplasmic reporter RNA species compared by Northern blotting, primer extension, and pulse-chase provided no evidence for altered processing induced by tripartite leader sequence. CONCLUSION: The tripartite leader sequence, known to facilitate translation of mRNA during the late phase of adenovirus infection, can also modulate mRNA export from the nucleus.