Callard G V, Mak P
Proc Natl Acad Sci U S A. 1985 Mar;82(5):1336-40. doi: 10.1073/pnas.82.5.1336.
An estrogen (E)-binding molecule having both occupied and unoccupied sites is restricted to nuclear subfractions in the testis of the spiny dogfish (Squalus acanthias). We investigated the hypothesis that a species characterized by high body-fluid osmolarity (1010 mosM) has an estrogen receptor (ER) that binds to chromatin with high affinity and consequently resists redistribution during tissue processing. Although the steroid binding and sedimentation properties of the Squalus nuclear ER conformed to those of classical ER, its elution maximum from DNA-cellulose was unusually high (0.55 M NaCl). A tendency to adhere tightly to cell nuclei was reflected in the high salt concentration (0.43 M KCl) required to extract 50% of the receptors from the nuclear compartment during homogenization and in the stability of the nuclear ER population in the presence of high concentrations of a nonionic solute (urea) or increased buffer volume. Mixing and redistribution experiments showed that nuclear ER could be quantitatively and qualitatively measured in cytosolic extracts, ruling out the possibility that soluble receptors were being masked. Although Squalus oviduct ER was similar to that of testis, ER in the testis and liver of a related elasmobranch (Potamotrygon) that maintains osmotic equilibrium at 300 mosM more closely resembled mammalian ER in its elution maximum from DNA-cellulose (0.22 M NaCl) and cytosolic/nuclear ratios in low-salt buffers. We conclude that Squalus testis has a single ER pool located exclusively in the nuclear compartment. These observations support a revised concept of steroid action and further indicate that the chromatin affinity of the hormone-ER complex is an important factor in determining subfractional distribution during tissue processing.
一种既有占据位点又有未占据位点的雌激素（E）结合分子局限于棘鲨（Squalus acanthias）睾丸的核亚组分中。我们研究了这样一个假说：一个以高体液渗透压（1010 mosM）为特征的物种具有一种雌激素受体（ER），该受体与染色质具有高亲和力，因此在组织处理过程中能抵抗重新分布。尽管棘鲨核ER的类固醇结合和沉降特性符合经典ER的特性，但其从DNA - 纤维素上的洗脱峰值异常高（0.55 M NaCl）。在匀浆过程中从核区室中提取50%的受体所需的高盐浓度（0.43 M KCl）以及在高浓度非离子溶质（尿素）存在或缓冲液体积增加时核ER群体的稳定性，都反映出其紧密粘附于细胞核的倾向。混合和重新分布实验表明，核ER可以在胞质提取物中进行定量和定性测量，排除了可溶性受体被掩盖的可能性。尽管棘鲨输卵管ER与睾丸的相似，但在300 mosM维持渗透平衡的相关板鳃亚类（Potamotrygon）的睾丸和肝脏中的ER，其从DNA - 纤维素上的洗脱峰值（0.22 M NaCl）以及在低盐缓冲液中的胞质/核比率更类似于哺乳动物的ER。我们得出结论，棘鲨睾丸有一个单一的ER池，仅位于核区室中。这些观察结果支持了类固醇作用的修订概念，并进一步表明激素 - ER复合物的染色质亲和力是决定组织处理过程中亚组分分布的一个重要因素。
