Identification of glucocorticoid- and cyclic AMP-responsive elements of the rat serine dehydratase gene: difference in responses of the transfected and chromosomal genes.

Transcription of the gene coding for serine dehydratase (SDH, EC 4.2.1.13) in rat liver is induced 3-4 fold by glucocorticoids plus glucagon, but not by either hormone alone. For identification of the DNA elements mediating the glucocorticoid- and cyclic AMP-regulated expression of the SDH gene, primary cultures of adult rat hepatocytes were transfected with a fusion gene consisting of the 2.15 kb 5'-flanking sequence of the SDH gene linked to the coding sequence of the gene for chloramphenicol acetyltransferase (CAT). CAT assay demonstrated that transient expression of the SDH-CAT fusion gene was inducible by either dexamethasone or dibutyryl cyclic AMP, but that the effects of these inducers were not additive or synergistic. These results suggest that some structural organization of the DNA influences the hormonal actions in regulation of gene expression.