INTEGRATION OF TETRACYCLINE REGULATION INTO A CELL-SPECIFIC TRANSCRIPTIONAL

The pancreas-specific transcriptional enhancer of the rat elastase I g ene was modified by substituting, in turn, each of its three individua l constitutive elements with the tetO element, which confers regulatio n by exogenous tetracycline in the presence of the hybrid tetO binding transactivator (tTA), Whereas the unmodified enhancer was active in t ransfected acinar tumor cells, substitution of individual elements wit h the tet-responsive element abolished activity, The modified enhancer s were reactivated in the presence of the tTA and, upon addition of te tracycline, were silenced, Thus, substitution of individual enhancer e lements renders the enhancer responsive to regulation by tetracycline. Moreover, the tTA activated levels were 2-8-fold greater than the unm odified enhancer, The acinar cell specificity of the unmodified enhanc er was retained; none of the tetO-substituted enhancers were activated by tTA in a variety of nonacinar cell lines, These results show that a foreign and artificial transcriptional activator, tTA, can be incorp orated into an enhancer to create a novel, efficient, and regulatable transcriptional control region whose cell specificity is retained.