The mechanism for steroid receptor-mediated regulation of target genes involves specific transactivation domains referred to as activation functions, the number of which varies depending on the particular steroid receptor. The availability of the activation domains is modulated by conformational changes induced by steroids and their analogues. In general, agonists induce changes in receptor structure that promote interactions with coactivators, thereby increasing transcription. On the other hand, some agonists and some antagonists induce changes in recep tor structure that facilitate receptor interactions with compressors, thus inhibiting transcription.1-10-1 However, antagonists generally inhibit transcriptional activity by occupying the receptor, thus preventing the steroid from binding.1-7-1
Cholesterol is the precursor for the steroid hormone family, which can be divided into six classes. The members of each class are similar structurally and in their mechanism of action. Steroids are responsible for regulating numerous processes within the body that are necessary for normal biological function.
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Harold F. Hintz
Cornell University, Ithaca, New York, U.S.A.
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