An oviduct-specific and enhancer-like element resides at about -3000 in the chicken ovalbumin gene

The chicken ovalbumin (Ov) gene is one of the best models to study tissue-specific gene regulation because it is only expressed in the oviduct. In this paper, a tissue-specific element was characterized by 5'-flanking region deletion in combination with in vivo gene electroporation (EP). Plasmids with varying lengths of truncated Ov 5'-flanking region fused to the Renilla luciferase reporter gene were transfected in vivo into oviduct, muscle, and pancreas. A chicken oviduct-specific and enhancer-like region (designated COSE) was implicated between -3100 and -2800. The COSE showed up-regulation of gene expression in oviduct, but not in muscle or in pancreas. The COSE region was further characterized by gel mobility shift assays using nuclear extracts from oviduct, pancreas and liver. With the region from -2900 to -2851, designated T2, there were two distinct protein-DNA complexes: one found only in oviduct extract and the other detected only in pancreas and liver. These data suggest a model where the regulation of Ov gene expression in the oviduct and non-oviduct tissues is exerted at least in part by the presence of protein modulators that bind to the COSE element.