We have investigated whether DNA regions present in the rabbit whey acidic protein (WAP) promoter/5′ flanking sequence could potentially confer. in vivo, high level expression or reporter genes. Transgenic mice were generated expressing a variant of human α1-antitrypsin, which has inhibitory activity against plasma kallikrein under the control of a 17.6 kbp DNA fragment located upstream of the rabbit WAP gene. Up to 10 mg/ml of active and correctly processed recombinant protein were detected in mouse milk, thus suggesting that the far upstream DNA sequences from the rabbit WAP gene might be useful for engineering efficient protein production in the mammary glands or transgenic animals.
