Polymorphic variation in the human protein C (PROC) gene promoter can influence transcriptional efficiency in vitro

The haplotype frequencies of two closely linked diallelic polymorphisms in the protein C(PROC) gene promoter were determined in the British population. In principle, differences in transcription efficiency between PROC promoter haplotypes could represent an additional risk factor in determining whether or not an individual already predisposed to venous thrombosis will come to clinical attention. In order to explore this postulate, transient transfection of human hepatoma cells with PROC promoter-luciferase reporter gene constructs was performed in vitro. In HepG2 cells, the T.....A haplotype exhibited at least a two-fold higher transcription efficiency than the C.....G haplotype. A sample of British protein C deficiency patients with recurrent venous thrombosis was then allelotyped by a combination of oligonucleotide discriminant hybridization and DNA sequencing. The frequency of the low expressing C.....G haplotype was found to be slightly yet not significantly higher in these patients (0.43) than in controls (0.35).