ABSTRACT

The papillomaviruses are small DNA tumor viruses which are epitheliotropic and productively infect only squamous epithelia. Transcription of papillomavirus genomes as a complex transcription unit allows the expression of multiple, overlapping genes to be differentially regulated through both transcriptional and posttranscriptional mechanisms. The chapter discusses the regulation of complex transcription units as it applies to the papillomaviruses. The prevailing theory of transcription termination downstream of mostpol II-transcribed genes is that termination is linked to cleavage at an upstream poly(A) site. The role of transcriptional pausing in the regulation of papillomavirus poly(A) site selection has not been studied. Most bovine papillomavirus type 1 pre-mRNAs are alternatively spliced, yielding a large number of different transcripts with different coding capacities. A variety of posttranscriptional regulatory elements are found in the 3' untranslated regions of viral and cellular genes and influence expression through effects on polyadenylation, nucleocytoplasmic transport, mRNA stability, and translation.