LACK OF GRADUAL REGULATION OF TETRACYCLINE-CONTROLLED GENE-EXPRESSIONBY THE TETRACYCLIN-REPRESSOR VP16 TRANSACTIVATOR (TTA) IN CULTURED-CELLS

Von Willebrand factor (vWF) is an essential multimeric protein for adh esion of platelets to an injured vessel wall. Endothelial cells secret e vWF by either a constitutive or a regulated pathway. It is unknown w hether the secretory partitioning of vWF is dependent on the level of VWF synthesis. We employed the widely applied tetracycline-controlled transactivator system (tTA) to study the regulation of vWF mRNA synthe sis in stably transfected Madin Darby kidney (MDCK-II) cells in a quan titative manner. Immunofluorescence staining with anti-vWF antibodies revealed that increasing the concentration of tetracycline resulted in a decreased number of MDCK-II cells that synthesize vWF. Apparently, tTA-regulated gene expression in an individual cell functions as an 'o n/off' system rather than regulating the level of gene expression in a dose-response manner, as reported previously. (C) 1997 Federation of European Biochemical Societies.