Bailly A, Sallas N, Milgrom E
J Biol Chem. 1977 Feb 10;252(3):858-63.
Dilution at 0 degrees of rat liver cytosol incubated with [3H]triamcinolone acetonide provoked an enhanced binding of steroid-receptor complexes to nuclei. The explanation of this phenomenon was found to be an "activation" of the complexes. Dilution acted by decreasing the concentration of a cytosol inhibitor. This reaction was irreversible at 0 degrees: once activated the complexes could not be reversed to the nonactivated state by the addition of inhibitor. The presence of hormone was necessary, since hormone-free receptor molecules could not be activated by dilution. Removal of the inhibitor did not lead to activation of all complexes: after 24 h a "plateau" was attained where 55 to 70% of the complexes were activated. The inhibitor was shown to be a low molecular weight molecule by dialysis, Sephadex G-25 chromatography, ammonium sulfate precipitation, and ultrafiltration. Thus [3H]triamcinolone acetonide-receptor complexes present in a cytosol from which the inhibitor had been removed by Sephadex G-25 chromatography became spontaneously activated at low ionic strength and at 0 degrees. The inhibitor is not a steroid (at least of usual polarity) since it cannot be extracted by methylene chloride or adsorbed by activated charcoal. It is thermostable (resists to 30 min at 100 degrees). Its removal by incubation with a cation exchange resin suggests that it may be positively charged, however it is not complexed by EDTA. This inhibitor must be distinguished from a previously described inhibitor of steroid-receptor complexes binding to nuclei. The latter compound has been shown in various systems to be responsible for an artifactual saturation of nuclear acceptor by steroid-receptor complexes. It inhibits the binding to nuclear acceptors of already activated complexes and is probably a macromolecule. It is thus different from the low molecular weight activation inhibitor described in the present paper.
在0℃下，用[³H]曲安奈德孵育大鼠肝脏胞质溶胶后进行稀释，会促使类固醇受体复合物与细胞核的结合增强。该现象的解释是复合物的“激活”。稀释通过降低胞质溶胶抑制剂的浓度起作用。此反应在0℃时不可逆：一旦被激活，复合物不能通过添加抑制剂恢复到未激活状态。激素的存在是必需的，因为无激素的受体分子不能被稀释激活。去除抑制剂并不会导致所有复合物被激活：24小时后达到一个“平台期”，此时55%至70%的复合物被激活。通过透析、葡聚糖凝胶G - 25柱色谱、硫酸铵沉淀和超滤表明抑制剂是一种低分子量分子。因此，经葡聚糖凝胶G - 25柱色谱去除抑制剂的胞质溶胶中存在的[³H]曲安奈德 - 受体复合物在低离子强度和0℃下会自发激活。该抑制剂不是类固醇（至少不是通常极性的类固醇），因为它不能被二氯甲烷萃取或被活性炭吸附。它耐热（在100℃下耐受30分钟）。与阳离子交换树脂孵育后去除该抑制剂表明它可能带正电荷，然而它不与EDTA络合。必须将这种抑制剂与先前描述的类固醇 - 受体复合物与细胞核结合的抑制剂区分开来。在各种系统中已表明后一种化合物会导致类固醇 - 受体复合物对核受体的人为饱和。它抑制已激活复合物与核受体的结合，并且可能是一种大分子。因此它与本文中描述的低分子量激活抑制剂不同。
