Regulation of the cytosolic aspartate aminotransferase housekeeping gene promoter by glucocorticoids, cAMP, and insulin

The cytosolic aspartate aminotransferase (cAspAT) is a ubiquitous enzyme that displays liver-specific hormonal regulation. In the hepatoma cell line Fao, both the activity and the mRNA level of cAspAT are increased by glucocorticoids. This effect is potentiated by cAMP and inhibited by insulin. Using in vivo run-on experiments, we showed that these effectors act at the transcriptional level. A cAspAT gene fragment containing 2405 bp of the promoter was sequenced. Deletion fragments of this promoter were inserted upstream of the CAT gene, and the regulation of their activity was assayed following transfection in Fao cells