Transcriptional control of bovine papillomavirus upstream regulatory region by linker scanning mutation

Abstract

The upstream regulatory region (URR) of the bovine papillomavirus type 1 (BPV-1) genome can function as a conditional transcriptional enhancer that can be specifically trans-activated by the viral E2 gene product. By the use of a linker scanning mutagenesis, the URR of BPV-1 was introduced double-stranded BamHI linker (5``-CGGATCCG-3``) at discrete locations without causing the addition or deletion of other sequences. These mutants of the URR were analyzed for their activity to enhance the activity of transcription from the promoters $P_{7940}$ and $p_{89}$ in the presence of the viral E2 gene product. The nucleotide sequences in the E2-responsive element 2 (E2RE2), even in one of the E2 binding site, were found to be replaceable. While the nucleotide sequences between the two paired E2 binding sites in E2RE1 were replaceable, the E2 binding site 10 and the 3`` boundary region of E2RE1 were proved to be necessarily critical to mediate the trans-activation. The finding that the replacements of the consensus recognition sequences for Sp1 and CCAAT-binding transcription factor (CTF) around the $P_{7940}$ promoter severely affected transcription indicates that the interaction between the viral E2 transactivator and the cellular transcription factors bound at the $P_{7940}$ promoter cis-elements are very important to activate the E2-responsive transcription.