Analysis of the Mechanism of Steroid Hormone Receptor-Dependent Gene Activation in Cell-Free Systems

I. Introduction STEROID hormones regulate the expression of specific gene networks and thereby exert a wide variety of effects on growth, development, and differentiation in higher eukaryotes (for reviews see Refs. 1–6). The hormonal signals are transduced to the target genes through specific, intracellular receptors. The ligand-free receptor is functionally inactive. The hormone response is triggered by the binding of a steroidal ligand to its cognate receptor, followed by the interaction of the hormonereceptor complex with specific enhancer sequences referred to as steroid response elements (SREs) at the target gene. The receptor regulates gene transcription presumably by interacting with the transcription machinery at the target promoter. During the last several years, good progress has been made toward unravelling the molecular mechanism of signal transduction by steroid hormones. The molecular cloning of virtually all known steroid receptor genes has been accomplished, and precise definition of vario...