A dominant-negative thyroid hormone receptor blocks amphibian metamorphosis by retaining corepressors at target genes
A dominant-negative thyroid hormone receptor blocks amphibian metamorphosis by retaining corepressors at target genes
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DOI：
10.1128/mcb.23.19.6750-6758.2003
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发表时间：
2003-10-01
影响因子：
5.3
通讯作者：
Shi, YB
中科院分区：
文献类型：
--
作者：
Buchholz, DR;Hsia, SCV;Shi, YB
两栖动物变态对甲状腺激素（T-3）的完全依赖性为研究T-3受体（TR）功能的分子机制提供了一个独特的脊椎动物模型。体外转录和发育表达研究已经导致TR在两栖动物发育中的双重功能模型，即，TRs在变态前蝌蚪中作为转录抑制因子，在变态过程中作为激活因子。我们研究的分子机制TR行动在T-3诱导的变态使用显性负性受体（dnTR）普遍表达的转基因非洲爪蟾。我们发现T-3诱导的T-3靶基因的激活和形态学变化在dnTR转基因动物中被阻断。通过使用染色质免疫沉淀，我们表明，dnTR结合到目标启动子，这导致保留辅阻遏物和持续组蛋白脱乙酰化T-3的存在下。因此，这些结果提供了直接在体内的证据，第一次通过dnTR改变基因表达的分子机制。dnTR介导的基因阻遏和抑制变态之间的相关性也支持TR在发育中的双重功能模型的一个关键方面：在T-3诱导的变态过程中，TR通过释放辅阻遏物和促进组蛋白乙酰化和基因激活来发挥激活剂的作用。
The total dependence of amphibian metamorphosis on thyroid hormone (T-3) provides a unique vertebrate model for studying the molecular mechanism of T-3 receptor (TR) function in vivo. In vitro transcription and developmental expression studies have led to a dual function model for TR in amphibian development, i.e., TRs act as transcriptional repressors in premetamorphic tadpoles and as activators during metamorphosis. We examined molecular mechanisms of TR action in T-3-induced metamorphosis by using dominant-negative receptors (dnTR) ubiquitously expressed in transgenic Xenopus laevis. We showed that T-3-induced activation of T-3 target genes and morphological changes are blocked in dnTR transgenic animals. By using chromatin immunoprecipitation, we show that dnTR bound to target promoters, which led to retention of corepressors and continued histone deacetylation in the presence of T-3. These results thus provide direct in vivo evidence for the first time for a molecular mechanism of altering gene expression by a dnTR. The correlation between dnTR-mediated gene repression and inhibition of metamorphosis also supports a key aspect of the dual function model for TR in development: during T-3-induced metamorphosis, TR functions as an activator via release of corepressors and promotion of histone acetylation and gene activation.