Oro A E, Ong E S, Margolis J S, Posakony J W, McKeown M, Evans R M
Howard Hughes Medical Institute, Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, California 92138.
Nature. 1988 Dec 1;336(6198):493-6. doi: 10.1038/336493a0.
Molecular cloning has demonstrated that the receptors for steroid, retinoid and thyroid hormones are part of a large superfamily of nuclear regulatory proteins. In vertebrates these molecules regulate diverse biological processes such as pattern formation, cellular differentiation and homeostasis. The universal necessity for embryonic and adult cells to respond to their external environment might mean that members of this family pre-date the divergence of vertebrates and invertebrates. We have screened a Drosophila genomic library for steroid receptor homologues using a human retinoic acid receptor complementary DNA as a hybridization probe. Several clones were recovered, one of which mapped to chromosomal position 77E1-2, the cytological location of the gap segmentation gene knirps. Sequence analysis of a cDNA clone representing the human retinoic acid receptor homologue showed similarity of the predicted protein to the vertebrate steroid receptors, as well as to the predicted knirps gene product. In situ hybridization of a cDNA probe to wild-type embryos revealed a uniform distribution of transcripts that were apparently maternally derived. Zygotic transcript accumulation begins in a broad anteroventral domain before the cellular blastoderm stage. At the cellular blastoderm stage two additional circumferential bands of transcript appear.
分子克隆技术已证明，类固醇、视黄酸和甲状腺激素的受体是核调节蛋白大家族的一部分。在脊椎动物中，这些分子调节多种生物学过程，如模式形成、细胞分化和体内平衡。胚胎细胞和成年细胞对外部环境做出反应的普遍必要性可能意味着该家族成员在脊椎动物和无脊椎动物分化之前就已存在。我们使用人类视黄酸受体互补DNA作为杂交探针，在果蝇基因组文库中筛选类固醇受体同源物。回收了几个克隆，其中一个定位于染色体位置77E1-2，即间隙分割基因knirps的细胞学位置。对代表人类视黄酸受体同源物的cDNA克隆进行序列分析，结果显示预测的蛋白质与脊椎动物类固醇受体以及预测的knirps基因产物具有相似性。将cDNA探针与野生型胚胎进行原位杂交，结果显示转录本呈均匀分布，显然是母源的。合子转录本积累在细胞胚盘阶段之前开始于一个宽阔的前腹区域。在细胞胚盘阶段，另外出现两条转录本的圆周带。
