Characterization of the Alu-rich 5'-flanking region of the human prothrombin-encoding gene: identification of a positive cis-acting element that regulates liver-specific expression.

The nt sequence of 6127 bp of sequence upstream of the human prothrombin-encoding gene (F2) has been determined. Since we previously characterized 417 bp of DNA immediately upstream from the transcription start point (tsp), 6544 bp of continuous flanking sequence are known. Eleven Alu repeat sequences present in this region comprise 45% of the sequence; other repetitive sequences were identified by searching GenBank. The tsp was found to be heterogeneous by exon mapping and primer extension analysis. To localize the cis-acting sequences responsible for the liver-specific expression of F2, hybrid cat genes were constructed with various lengths of F2 5'-flanking region cloned upstream from a promoterless cat gene. After transfection into HepG2 and HeLa cells, it was inferred that the region between nt -1101 and -798 was required for synthesis in HepG2 cells; no synthesis was observed using these constructs in HeLa cells. Two sequences for known liver-specific or regulatory cis-acting sequences were identified in this region.