Transformation of glucocorticoid-receptor complex from rat thymocytes and its accumulation in chromatin in a cell-free system

Abstract

The accumulation of glucocorticoid-receptor complex from rat thymocyte cytosol in a thymocyte chromatin preparation has been studied. A thymocyte 100 000 × g supernatant was prepared and the receptor stabilized by the addition of glycerol until 40%. Tritiated glucocorticoid-receptor complex was formed by incubation of this solution with tritiated glucocorticoids at −5°C. The chromatin accumulated part of the complex at incubations at 4°C. Receptor without hormone was not accumulated in the chromatin. The accumulation from cytosol diluted and preincubated at 4°C prior to the addition of the chromatin occurred with a high rate, whereas a low rate was seen without preincubation. This indicated a transformation of the complex during the preincubation. This transformation was found to be obligatory for the accumulation and to be promoted by dilution of the supernatant and by high ionic strength. The transformed and the untransformed complexes differed with respect to partition coefficients in an aqueous dextran-polyethylene glycol two-phase system and in their behaviour during adsorptions with dextran-coated charcoal, where great loss of transformed complex was observed. The accumulation of complex in the chromatin was found to be unsaturable in the concentration interval studied (0.07–0.25 nM).