Mechanism of gene expression by androgen receptor in rat and mouse submandibular glands

类固醇受体从非转化状态到转化状态的转换，称为转化，被认为是类固醇激素作用的关键过程。转化后的受体激活靶细胞中的特定基因。类固醇激素受体从DNA非结合状态到DNA结合状态的转变可以通过短暂加热、暴露于盐或ATP以及凝胶层析来诱导。一般来说，未转化的受体是通过添加硫酸鱼精蛋白选择性地沉淀的。我们发现，负责未转化受体和鱼精蛋白相互作用的成分是一个88 kDa的蛋白，该蛋白的氨基酸组成与HeLa细胞和酵母的热休克蛋白90的氨基酸组成几乎相同。类固醇转化的受体复合体与核受体结合，但染色质的结构如何改变对基因表达的影响尚不清楚。[~(3 H)]雄激素标记的胞浆雄激素受体与小鼠颌下腺的粗核发生相互作用，激活该受体是相互作用的前提。给雌性小鼠体内注射雄激素后，从颌下腺组织中提纯的细胞核具有放射活性，进一步用微球菌核酸酶消化标记的提纯细胞核。雄激素受体存在于含有单核小体和双核小体的活性染色质组分中。通过体外交换实验，在微球菌核酸酶消化后的溶解部分中发现了与完整男性染色质结合部位相关的内源性雄激素受体复合体，而在雌性体内没有发现这种复合体。这些结果表明，雄激素受体移位到细胞核，并与染色质相关，这种联系对微球菌核酸酶优先敏感。

Conversion of steroid receptors from the nontransformed to transformed state, called transformation, is thought to be a key process of the steroid hormone action. Transformed receptors activate the specific genes in target cells. Transformation of steroid hormone receptor from a DNA-unbound state to a DNA-bound state can be induced by brief heating, exposure to salt, or ATP, and gel chromatography. IN general, nontransformed receptor is precipitated selectively by the addition of protamine sulfate. We found that the component responsible for the interection between the nontransformed receptor and protamine is an 88-kDa protein and this 88-kDa protein is almost the same as those of heat-shock protein 90 of hela cells and yeast for the amino acid composition.The steroid-transformed receptor complex interacts with nuclear acceptor sites, but it remains unclear how the structure of chromatin is changed for gene expression. Cytosol androgen receptor prelabeled with [^3H]androgen interacted with the crude nuclei in mouse submandibular gland and activation of the receptor was prerequisite for this interaction. After in vivo administration of [^3H]androgen to female mice, redioactivities were found in the nuclei purified from submandibular gland tissues and the [^3H]androgen-labeled purified nuclei were further digested with micrococcal nuclease. the androgen receptor was found in solubilized, active chromatin fractions which contained mono- and dinucleosomes. By an in vitro exchange assay, endogenous androgen-receptor complexes associated with chromatin binding sites in intact males were found in the solubilized fraction after micrococcal nuclease digestion, whereas such complexes were not found in females. These results suggest that the androgen receptors translocated to the nuclei and became associated with chromatin and that this association preferentially sensitive to micrococcal nuclease.