The <i>cis</i>‐element <i>CE‐LPH1</i> of the rat intestinal lactase gene promoter interacts in vitro with several nuclear factors present in endodermal tissues

Abstract

We have shown by electrophoretic mobility shift assays that the nucleotide sequence CE-LPH1, centred at position -49 with respect to the transcription start site of the rat gene encoding intestinal lactase-phlorizin hydrolase, interacts in vitro with nuclear proteins present in the jejunum of suckling animals. Proteins binding to this element were also found in organs of endodermal origin that do not (or no longer) express lactase-phlorizin hydrolase, i.e. the colon, lung and the liver, but not in the brain. However, a DNA-protein interaction was hardly detected with nuclear extracts prepared from adult tissues, although typical factors binding to the Sp1 binding site were detected at the adult stage as in the sucklings. Southwestern blotting experiments conducted with nuclear extracts prepared from the tissues of suckling rats indicated that CE-LPH1 interacts with several factors in the jejunum, colon, lung and the liver. Some of these DNA-binding proteins are specifically expressed in the jejunum or in the liver, whereas others seem to be shared with the colon and the lung. Hence, the cis-element CE-LPH1 located in close vicinity to the pseudo-TATA-box of the intestinal lactase-phlorizin hydrolase gene promoter interacts in vitro with a family of nuclear proteins which may represent markers of the endodermal lineage predominantly expressed prior to weaning.