The summing up
The contributions of this symposium reflect a great variety in approach, at many different levels of organisation, ranging from fragments of genes to interactional behaviour between two animals. However, the focal questions remain what they have been for some time- what are the state, the fate and the roles of steroid-receptor complexes that have gained access to the cell nucleus. This was apparent from the introductory remarks to the symposium from Dr. W. I. P. Mainwaring, the results of his experiments pointing to the nuclear matrix as an important site for the initiation by androgen of DNA replication. Indeed, Barrack and Coffey (1980) already have shown that the nuclear matrix could serve as a binding site for hormone-receptor complexes and in the light of Mainwaring’s experiments, this could be significant. However, hormone-receptor complexes show a remarkable propensity to bind to many different moieties. One need mention only DNA and non-histone basic proteins of the nucleus as putative acceptor sites for the A and B sub-units of the chick oviduct progesterone receptor complexes; the differentiation of nuclear bound complexes according to whether or not they can be extracted in 0.4M KC1 and the occurrence in nuclei of unfilled steroid binding sites recently discussed by Carlson and Gorski (1980). Although it would be conceptually tidy to have only one form of acceptor, it is not necessary and in view of the plethora of possibilities it seems unlikely. In cytoplasm too, the association of the hormone-receptor complexes with other moieties can be important.
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