Studies on the P3 promoter of bovine papillomavirus type-1

Abstract

Analysis of CAT plasmids containing BPV-1 (Bovine Papillomavirus Type-1) P3 promoter allowed identification of the promoter activity and E2 transactivator required for maximal transcription of the P3. The results showed that the P3 is very weak promoter and E2 transactivator requires for the maximal transcription of P3 promoter in a BPV-1 URR (Upstream Regulatory Region) dependent manner. It is suggested that an autoregulatory circuit based on the E2 protein is crucial. Furthermore, we removed portions of the 5`` or 3`` flanking sequence of P3 promoter using an exonuclease BAL 31 and characterized the transcriptional activity of the resulting deletion CAT mutants. This analysis showed that an upstream sequence, delimited by -320 (nt 576) bp and -94 (nt 802) bp with respect to the mRNA cap site, is required for the functional activity of P3 promoter. In contrast, very low levels of transcription were directed by constructs that contained 162 bp (-94 to +1 bp) of 5`` non-coding sequence, suggesting that the additional sequence (-302 to -94) further 5``exert a quantitative effect on transcription. Within this 226 bp region of P3 promoter, there are several sequence motifs, $ACCN_6GGT$, SV40 enhancer core sequence and ATF binding site, highly analogous to the consensus sequence of binding sites for transcriptional regulatory proteins.