ETS TRANSCRIPTION FACTORS BIND AND TRANSACTIVATE THE CORE PROMOTER OFTHE VON-WILLEBRAND-FACTOR GENE

von Willebrand factor (VWF) gene expression is restricted to endotheli al cells and megakaryocytes. Previous results demonstrated that basal transcription of the human vWF gene is mediated through a promoter loc ated between base pairs -89 and +19 (cap site: +1) which is functional in endothelial and non endothelial cells, Two DNA repeats TTTCCTTT co rrelating,vith inverted consensus binding sites for the Ets family of transcription factors are present in the -56/-36 sequence, In order to analyse whether these DNA elements are involved in transcription, hum an umbilical vein endothelial cells (HUVEC), bovine calf pulmonary end othelial cell line (CPAE), HeLa and COS cells mere transfected with co nstructs containing deletions of the -89/+19 fragment, linked to the c hloramphenicol acetyl transferase (CAT) reporter gene, The -60/+19 reg ion exhibits significant promoter activity in HUVEC and CPAE cells onl y, The -42/+19 fragment is not active, Mutations of the -60/+19 promot er fragment in the 5' (-56/-49) Ets binding site abolish transcription in endothelial cells whereas mutations in the 3' (-43/ -36) site does not, The -60/-33 fragment forms three complexes with proteins from HU VEC nuclear extracts in electrophoretic mobility shift assay which are dependent on the presence of the 5' Ets binding site, Binding of reco mbinant Ets-1 protein to the -60/-33 fragment gives a complex which al so depends on the 5' site, The -60/+19 VWF gene core promoter is trans activated in HeLa cells by cotransfecting with Ets-1 or Erg (Ets-relat ed gene) expression plasmids, In contrast to the wild type construct, transcription of the 5' site mutants is not increased by these express ed proteins, The results indicate that the promoter activity of the -6 0/+19 region of the vWF gene depends on transcription factors of the E ts family of which several members like Ets-1, Ets-2 and Erg are expre ssed in endothelium. Cotransfection of Ets-1 and Erg expression plasmi ds is sufficient to induce the -60/+19 vWF promoter activity in HeLa c ells.