The role of the 5'-flanking region in the cell-specific transcription of the human von Willebrand factor gene.

Abstract

Transcriptional regulation of the human von Willebrand factor (vWF) gene was investigated in calf pulmonary artery endothelial (CPAE), HeLa, COS 7 and Hep G2 cells. Various lengths of flanking sequences extending up to 2123 bp 5' of the transcription initiation site and containing 19 bp of the first exon, were linked to the bacterial chloramphenicol acetyltransferase (CAT) gene and these constructs were assayed in transient transfection assays. Sequences up to 89 bp upstream of the cap site showed transcriptional activity in all cell types. Sequences between -147 and -419 bp markedly reduced CAT activity in CPAE cells and abolished it in other cell lines. A domain from -592 to -810 bp generated low levels of expression only in CPAE cells. This transcriptional activity was repressed with constructs containing 1041 to 1240 bp upstream of the cap site. Endothelial cell-specific transcription was restored by a construct that contained 1286 bp upstream of the cap site. The additional 46 bp upstream of the negative regulatory domain were within the 5' end of an inverse human Alu-family DNA repeat. RNAase-protection assays confirmed the correct transcriptional initiation. The sequence between -89 and -420 contained at least one negative regulatory element able to repress the CAT gene expression controlled by the heterologous thymidine kinase promoter in all cell types. A construct that included the sequence from -89 to -1286 bp increased the transcriptional activity directed by the thymidine kinase promoter only in CPAE cells. These results indicate that negative and positive elements in the 5'-flanking region interact to regulate vWF gene expression.