Coordinate regulation of bovine prion protein gene promoter activity by two Sp1 binding site polymorphisms

Relationships between insertion/deletion (Ins/Del) polymorphisms of the bovine prion protein gene (PRNP) promoter and bovine spongiform encephalopathy (BSE) susceptibility have been reported. Our previous study has shown that polymorphisms of -6C-->T included in the specific protein 1 (Sp1) site in the 5'-flanking region of bovine PRNP influence the promoter activity of bovine PRNP. The present study shows that 12 and 23bp Ins/Del polymorphisms in the upstream region and an additional polymorphism (-47C-->A) in the Sp1 binding site coordinately affect the promoter activity. Reporter gene assays demonstrated that the bovine PRNP promoter containing -47A and 23bp Del/12bp Ins or 23bp Ins/12bp Ins showed lower promoter activity compared with other haplotypes (23bp Del/12bp Ins or 23bp Ins/12bp Del with -47C) or the wild-type haplotype (23bp Del/12bp Del with -47C). Furthermore, gel shift assays showed that the binding activity of Sp1 to the PRNP promoter was influenced by both polymorphisms with corresponding effects on the promoter activity. The coordinate regulation of the bovine PRNP promoter suggests the two Sp1 binding site polymorphisms control Sp1 binding to the PRNP promoter and its activity.