On the whole, the question as to how steroid hormones act to induce the transcription of specified genes is not much more understood today than it was 15 years ago, but considerable progress has been made during this time to bring us a step closer to unravelling the mysteries surrounding the mechanism of hormonal gene activation. Hopefully, further studies in the three fields described (i.e. DNA/receptor binding experiments, gene-transfer experiments, and in vitro transcriptional studies) will bring in enough information for a complete story to be told one day. As to the questions asked in the introduction of this review, there appear to be sequences around inducible genes that render them sensitive to hormone administration. These sequences could be arranged in appropriate chromosomal structures flanking the gene region particularly at the 5′ end. As to whether these sequences bind the hormone/receptor complex, the experiments with the MMTV proviral DNA (17, 21–23) and the ovalbumin gene (27) appear to provide an affirmative answer. But the answer to whether this binding is responsible for the gene activation must await future experimentation. In vitro transcriptional studies specially designed with the hormone/receptor/DNA complex may be useful in answering this question.

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