Sp1 is critical for basal and E2-transactivated transcription from the bovine papillomavirus type 1 P89 promoter

The bovine papillomavirus type 1 (BPV-1) long control region (LCR) contains at least three consensus binding sites for the transcription factor Sp1 at nucleotides (nt) 7800, 7833 and 7854. A high basal-level P89 expression vector consisting of an origin-deleted LCR fused to the chloramphenicol acetyltransferase (CAT) gene was utilized to determine the role of these Sp1 sites in the regulation of transcription from the BPV-1 P89 promoter. The three Sp1 sites were capable of binding Sp1 in vitro. Mutation of these sites in the background of the origin-deleted LCR-CAT or a wild-type LCR-CAT construct resulted in decreased basal expression from P89. In addition, mutation of the Sp1 sites in the wild-type background caused a reduction in E2-transactivation potential. These data illustrate the importance of these Sp1 sites in regulating both basal and E2-transactivated P89 expression.