Glutamine synthetase gene transcription in cultured 3T3-L1 adipocytes: regulation by dexamethasone, insulin and dibutyryl cyclic AMP.

We have investigated the regulation of glutamine synthetase (GS) mRNA synthesis in cultured 3T3-L1 adipocytes. Specific mRNA synthesis (transcription) was analyzed by measuring elongation of transcripts in isolated nuclei. Transcription rate was assayed by hybridization of newly synthesized [32P]RNA to a GS cDNA. GS transcription rate increased more than 100-fold during adipocyte differentiation and was inhibited more than 90% by alpha-amanitin. In 3T3-L1 adipocytes dexamethasone stimulated GS gene transcription while insulin and dibutyryl cAMP decreased GS gene transcription.