Ijiri S, Berard C, Trant J M
Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore 21202, USA.
Mol Cell Endocrinol. 2000 Jun;164(1-2):169-81. doi: 10.1016/s0303-7207(00)00228-8.
Cytochrome P450 aromatase (P450arom; CYP19) mediates the conversion of androgens to estrogens and its activity has been found in all vertebrates studied to date. This study describes the full-length cDNA encoding the ovarian form of P450arom and the differences in the 5'-untranslated region (5'-UTR) of the extra-gonadal P450arom transcript expressed by the Atlantic stingray (Dasyatis sabina). Elasmobranchs (cartilaginous fishes such as sharks, rays and skates) diverged from the other vertebrates more than 350 million years ago, therefore the stingray P450arom cDNA may represent an ancient form of this gene. Northern blot analysis showed that the ovarian follicle expressed transcripts of 3.1 and 1.7 kb in size which correspond to the clones isolated from a stingray ovarian follicle cDNA library. Both transcripts consisted of an identical 1.5 kb coding region and a 41 bp 5'-UTR, however the 3'-UTRs differed in the use of the most proximate and the most distal of four polyadenylation signals. COS cells transfected with the 1.7 kb cDNA had twice the aromatase activity as cells transfected with the 3.1 kb cDNA. The coding region of the cDNA predicted a 58.5 kDa protein which consisted of 511 residues. Alignment of the stingray protein indicates that the P450arom is equally identical (53-59%) to all other vertebrate forms of P450arom characterized to date, thus indicating a common ancestry. The evolutionary relationship of the stingray form of P450arom clearly predates the other forms and belongs to a unique lineage. Transcripts of P450arom were expressed in ovarian follicles (of all sizes), the testis, the pituitary, in all sections of the brain, and in the kidney. The extra-gonadal transcripts appear to encode a protein identical to the ovarian form, however, the 5'-UTR was 657 bp longer presumably due to the transcription of an untranslated 'first exon' as seen in the mammalian form of this gene.
细胞色素P450芳香化酶（P450arom；CYP19）介导雄激素向雌激素的转化，并且在迄今研究过的所有脊椎动物中均发现其活性。本研究描述了编码卵巢型P450arom的全长cDNA，以及大西洋黄貂鱼（Dasyatis sabina）所表达的性腺外P450arom转录本5'-非翻译区（5'-UTR）的差异。板鳃亚纲动物（如鲨鱼、鳐鱼和魟鱼等软骨鱼类）在3.5亿多年前就与其他脊椎动物分道扬镳，因此黄貂鱼P450arom cDNA可能代表了该基因的一种古老形式。Northern印迹分析表明，卵巢卵泡表达大小为3.1 kb和1.7 kb的转录本，这与从黄貂鱼卵巢卵泡cDNA文库中分离出的克隆相对应。两种转录本均由相同的1.5 kb编码区和41 bp的5'-UTR组成，然而3'-UTR在四个聚腺苷酸化信号中最靠近和最远端信号的使用上有所不同。用1.7 kb cDNA转染的COS细胞的芳香化酶活性是用3.1 kb cDNA转染的细胞的两倍。该cDNA的编码区预测出一种由511个残基组成的58.5 kDa蛋白质。黄貂鱼蛋白质的比对表明，P450arom与迄今已鉴定的所有其他脊椎动物形式的P450arom具有相同的同源性（53 - 59%），从而表明它们有共同的祖先。黄貂鱼形式的P450arom的进化关系明显早于其他形式，并且属于一个独特的谱系。P450arom的转录本在（各种大小的）卵巢卵泡、睾丸、垂体、大脑的所有区域以及肾脏中均有表达。性腺外转录本似乎编码一种与卵巢型相同的蛋白质，然而，5'-UTR长657 bp，这可能是由于该基因的哺乳动物形式中所见的一个非翻译“第一外显子”的转录所致。
