Regulated RNA Processing and RNA Transport during Adenovirus Infection

Adenovirus (Ad) gene expression involves regulation both of RNA processing and RNA transport. The major late transcription unit (MLTU) in particular requires complex differential splicing and polyadenylation to produce its full array of mRNA and the pattern of processing changes as infection proceeds. Many MLTU mRNAs cannot reach the cytoplasm effectively without viral functions, probably because they are recognized by host nuclear retention mechanisms. Infection produces changes to the activity of cellular splicing factors and polyadenylation factors so altering the relative recognition of competing RNA processing sites as infection proceeds. In addition, three Ad proteins, E1B 55K, E4 Orf3, and E4 Orf6 are involved in posttranscriptional regulation. These directly or indirectly alter the pattern of MLTU splicing, facilitate late RNA export, and alter the distribution of cellular antigens within the nucleus.