The type III 5-deiodinase in Rana catesbeiana tadpoles is encoded by a thyroid hormone-responsive gene.
The type III 5-deiodinase in Rana catesbeiana tadpoles is encoded by a thyroid hormone-responsive gene.
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DOI：
10.1210/endo.136.10.7664662
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发表时间：
1995-10
期刊：
影响因子：
4.8
通讯作者：
K. Becker;Mark J. Schneider;J. Davey;V. Galton
中科院分区：
文献类型：
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作者：
K. Becker;Mark J. Schneider;J. Davey;V. Galton
我们最近报道，非洲爪蟾互补DNA（cDNA），XL-15，编码一个硒蛋白，是一个5-脱碘酶（5D）。XL-15代表了一个在这个物种中被甲状腺激素上调的基因。我们现在报道从牛蛙（Rana catesbeiana，RC）cDNA文库中分离RC 5D（RC 5D）的cDNA。RC 5D是一个1534个碱基对的cDNA，其编码区与XL-15具有78%的同一性，包括TGA密码子，其在XL-15中编码硒代半胱氨酸，以及位于3 '非翻译区的推定硒代半胱氨酸插入序列（SECIS）。体外合成的RC 5D转录物注射到非洲爪蟾卵母细胞后诱导5D活性。RC 5D与RC组织中的2.2-腺苷酸酶信使RNA（mRNA）种类杂交。研究了未经处理和T3处理的变态前蝌蚪的10个组织中RC 5D的表达。RC 5D mRNA转录和5D活性在大多数组织中检测到，并且两者的水平在T3刺激的蝌蚪中大大增加。此外，RC 5D mRNA转录水平与5D活性密切相关，但与5 '-脱碘酶（5' D）活性无关。蝌蚪暴露于T3 4天后，5 ′ D没有增强。T3对RC 5D基因表达的上调在第V阶段的蝌蚪中是明显的，但被发现是短暂的。RC 5D转录水平和5D活性分别在T3暴露2-3天和5天后最高，但在10天后下降到与未暴露蝌蚪相当的水平。可以得出结论，RC 5D编码的硒蛋白是一个5D，它代表了一个基因，是由T3上调。本文提出的研究结果的基础上，它表明，5D系统在调节细胞内的T3水平在发展中的蝌蚪中起着重要的作用。
We have recently reported that the Xenopus laevis complementary DNA (cDNA), XL-15, encodes a selenoprotein that is a 5-deiodinase (5D). XL-15 represents a gene that is up-regulated by thyroid hormone in this species. We now report the isolation from a Rana catesbeiana (RC) cDNA library of a cDNA for the RC 5D (RC5D). RC5D a 1534-base pair cDNA that exhibits 78% identity to XL-15 in the coding region, including the TGA codon, which in XL-15 encodes selenocysteine, and a putative selenocysteine insertion sequence (SECIS) located in the 3'-untranslated region. Transcripts of RC5D, synthesized in vitro, induce 5D activity after their injection into Xenopus laevis oocytes. RC5D hybridizes to a 2.2-kilobase messenger RNA (mRNA) species in RC tissues. The expression of RC5D was studied in 10 tissues from untreated and T3-treated premetamorphic tadpoles. RC5D mRNA transcripts and 5D activity were detected in most tissues examined, and the levels of both were greatly increased in T3-stimulated tadpoles. Furthermore, the levels of RC5D mRNA transcripts correlated closely with 5D, but not with 5'-deiodinase (5'D), activity. 5'D was not enhanced by a 4-day exposure of the tadpoles to T3. The up-regulation of RC5D gene expression by T3 was demonstrable in tadpoles by stage V, but was found to be transient. The levels of RC5D transcripts and 5D activity were highest after 2-3 days and 5 days of T3 exposure, respectively, but had fallen by 10 days to levels comparable to those in unexposed tadpoles. It is concluded that RC5D encodes a selenoprotein that is a 5D, and it represents a gene that is up-regulated by T3. On the basis of the findings presented herein, it is suggested that the 5D system plays a major role in regulating intracellular T3 levels in developing tadpoles.