A 700-BP FRAGMENT OF THE HUMAN ANTITHROMBIN-III PROMOTER IS SUFFICIENT TO CONFER HIGH, TISSUE-SPECIFIC EXPRESSION ON HUMAN APOLIPOPROTEIN A-II IN TRANSGENIC MICE

The human antithrombin III-encoding gene (hAT-III) promoter (phAT-III) was used to generate transgenic mice producing a human hepatic apolip oprotein, apolipoprotein A-II (hApoA-II). Integration of the transgene into the mouse genome resulted in the efficient production of hApoA-I I in plasma, reaching up to 0.40 g/l in two transgenic lines. The huma n ApoA-II mRNA was detected at high levels, both in the liver and in t he kidney of transgenic mice. The rat AT-III gene shows the same expre ssion pattern. In contrast, as previously described, the same promoter permitted the expression of the SV40 large T antigen only in the live r of transgenic mice. In view of the extra-hepatic distribution of the ApoA-II mRNA, a preliminary characterization of the hAT-III proximal promoter (phAT-III), driving the expression of the transgene, was real ized. Using DNase I footprinting analysis with liver nuclear extracts, four protected regions (I-IV) were identified in the first 175 bp of the 5' region of hAT-III. Electrophoretic mobility shift assays perfor med with liver and kidney nuclear extracts indicate that region III (n ucleotides (nt) -67 to -90) interacts with the liver-enriched HNF4 nuc lear factor. Furthermore, our data suggest that region I(nt - 123 to - 138) interacts with the liver-enriched HNF3 transcription factor fami ly, both in liver and kidney. Taken together, these results demonstrat e that phAT-III is a useful tool to create transgenic mice producing h igh plasma levels of a human apolipoprotein due to expression of the t ransgene in liver and kidney. Interestingly, our data suggest that, in both organs, common pathways are involved in the control of phAT-III activity.