THE CIS-ELEMENT CE-LPH1 OF THE RAT INTESTINAL LACTASE GENE PROMOTER INTERACTS IN-VITRO WITH SEVERAL NUCLEAR FACTORS PRESENT IN ENDODERMAL TISSUES

We have shown by electrophoretic mobility shift assays that the nucleo tide sequence CE-LPH1, centred at position -49 with respect to the tra nscription start site of the rat gene encoding intestinal lactase-phlo rizin hydrolase, interacts in vitro with nuclear proteins present in t he jejunum of suckling animals. Proteins binding to this element were also found in organs of endodermal origin that do not (or no longer) e xpress 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 t ypical factors binding to the Sp1 binding site were detected at the ad ult stage as in the sucklings. Southwestern blotting experiments condu cted 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 spec ifically 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-L PH1 located in close vicinity to the pseudo-TATA-box of the intestinal lactase-phlorizin hydrolase gene promoter interacts in vitro with a f amily of nuclear proteins which may represent markers of the endoderma l lineage predominantly expressed prior to weaning.