Hormonal Mechanisms in Regulation of Gene Expression

Abstract

Research on the question of how genes are regulated in mammalian cells has accelerated rapidly in the last decade, with much attention being paid to systems in which gene expression is regulated by hormones. Virtually all the hormones have been implicated in this facet of regulation, including those acting via cyclic AMP as intracellular mediator; indeed, there is now firm evidence that cyclic AMP acts to regulate synthesis of specific enzymes in mammalian cells (1,2) as well as in bacteria (3,4). Our recent work, however, has involved hormones which appear to act independently of cyclic AMP, at least in the experimental system we employ. We shall review here some of our recent observations on the mechanisms involved in the stimulation of synthesis of a specific enzyme by the steroid hormone, hydrocortisone, as well as by the polypeptide hormone, insulin. As might be anticipated by the difference in structure of these hormones, we conclude that their mechanisms of enzyme induction are quite different, the steroid acting via a transcriptional mechanism and insulin clearly acting at some post-transcriptional stage of enzyme synthesis. Details of experimental approaches not fully described here can be found in our earlier publications on this work (4–7).