Characterization of the human blood coagulation factor X promoter

Blood coagulation Factor X is a serine protease required for both the intrinsic and extrinsic pathways of coagulation. The gene for Factor X spans 27 kilobases and is located on chromosome 13, in close proximity to the gene encoding Factor VII. Expression of Factor X is restricted to the liver. We have characterized the human Factor X promoter by mapping the start sites of transcription and carrying out a functional analysis of the promoter. The first 279 base pairs (bp) of 5'-flanking sequence upstream from the first AUG are sufficient to confer maximal promoter activity in HepG2 cells. Protein-binding sites within the 279-bp fragment are defined using gel mobility shift assays. Mutagenesis of two specific sequences within the 279-bp fragment (CCAAT at -120 to -116, and ACTTTG at -56 to -51), results in loss of ability to bind proteins from a HepG2 nuclear extract, and profound reduction in promoter activity of the 279-bp fragment. We conclude that these two protein-binding sites are critical for the activity of the Factor X promoter.