Kostrouch Z, Kostrouchova M, Rall J E
Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
Proc Natl Acad Sci U S A. 1995 Jan 3;92(1):156-9. doi: 10.1073/pnas.92.1.156.
The large family of steroid/thyroid hormone receptor (STR) genes has been extensively studied in vertebrates and insects but little information is available on it in more primitive organisms. All members possess a DNA binding domain of zinc fingers of the C2, C2 type. We have used the polymerase chain reaction with degenerate oligonucleotide primers covering this region to clone three distinct members of this family from the nematode Caenorhabditis elegans. All three belong to the retinoic acid receptor (RAR), thyroid hormone receptor subfamily of genes. The cDNA of one of these clones shows such a high homology to DHR3, an early ecdysone response gene found in Drosophila, and MHR3, identified in Manduca sexta, that we have termed it CHR3. Furthermore, the C-terminal portion of the deduced protein sequence shows a box containing eight identical amino acids among CHR3, DHR3, and MHR3 suggesting an identical specific ligand for these proteins. CNR8 shows homology to NAK1, and CNR14 has homology to both the RAR-gamma 1 gene and to another ecdysone response gene, E78A. Neither of the latter two cDNAs is a clear homologue of any known gene and each is distinctive. All of these genes are expressed varyingly in both larval and adult stages of nematode development as shown by Northern blot analyses. These data demonstrate that the STR family of genes is represented in a nematode whose ancestor appeared well before the branching that gave rise to the Arthropoda and Chordata.
类固醇/甲状腺激素受体（STR）基因大家族在脊椎动物和昆虫中已得到广泛研究，但在更原始的生物中相关信息却很少。所有成员都拥有C2、C2型锌指的DNA结合结构域。我们使用覆盖该区域的简并寡核苷酸引物通过聚合酶链反应从线虫秀丽隐杆线虫中克隆出该家族的三个不同成员。这三个成员均属于视黄酸受体（RAR）、甲状腺激素受体基因亚家族。其中一个克隆的cDNA与在果蝇中发现的早期蜕皮激素反应基因DHR3以及在烟草天蛾中鉴定出的MHR3具有高度同源性，因此我们将其命名为CHR3。此外，推导的蛋白质序列的C末端部分显示在CHR3、DHR3和MHR3中有一个包含八个相同氨基酸的框，这表明这些蛋白质具有相同的特异性配体。CNR8与NAK1具有同源性，CNR14与RAR-γ1基因以及另一个蜕皮激素反应基因E78A都具有同源性。后两个cDNA都不是任何已知基因的明确同源物，且各自都很独特。如Northern印迹分析所示，所有这些基因在秀丽隐杆线虫发育的幼虫和成虫阶段均有不同程度的表达。这些数据表明，STR基因家族存在于一种线虫中，该线虫的祖先早在节肢动物和脊索动物分支之前就已出现。
