Modulation of the transferred mouse 26K casein gene in mouse L cells by glucocorticoid hormone

The cloned 26K casein gene was transferred to mouse L-cells and its expression was measured by Northern blot hybridization. When the lambda clone with 5'- and 3'-flanking sequences was transferred, transcripts were detected without glucocorticoid, but in the presence of glucocorticoid, the level of the transcripts of heterogeneous sizes increased and their pattern was similar to that observed in the mammary glands of non-lactating mice. When the 6.7 kb EcoRI fragment containing most of the coding region was transferred, putative precursor and mature mRNAs were detected without glucocorticoid. Surprisingly, with the addition of glucocorticoid, the level of the transcripts greatly decreased. The presence of multiple sequences responsible for glucocorticoid receptor binding was detected in the 5'-flanking region of the gene in a competition assay using the subfragments of casein gene and on sequence analysis. These results suggest that the 26K casein gene has multiple regulatory domains which interact with glucocorticoid receptors, and these domains may play different roles in the regulation of the casein gene.