Tissue- and gene-specific recruitment of steroid receptor coactivator-3 by thyroid hormone receptor during development
Tissue- and gene-specific recruitment of steroid receptor coactivator-3 by thyroid hormone receptor during development
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DOI：
10.1074/jbc.m503999200
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发表时间：
2005-07-22
影响因子：
4.8
通讯作者：
Shi, YB
中科院分区：
文献类型：
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作者：
Paul, BD;Buchholz, DR;Shi, YB
许多结合核激素受体的辅活化剂已被分离并在体外表征。相对较少的研究已经解决了这些辅助因子在体内的发育作用。以两栖类变态对甲状腺激素（T-3）的完全依赖性为模型，研究了类固醇受体辅激活因子3（SRC 3）在甲状腺激素受体（TR）激活基因中的作用。首先，表达分析表明SRC 3在所分析的所有蝌蚪器官中表达。此外，在自然以及T-3诱导的变态过程中，SRC 3在尾部和肠道中均上调，这两个器官在变态过程中经历了广泛的转变，也是目前研究的重点。然后，我们进行染色质免疫沉淀试验，以调查SRC 3是否被招募到内源性T-3靶基因在体内发育的蝌蚪。令人惊讶的是，我们发现，SRC 3招募的基因和组织依赖性的方式，以靶基因的TR，无论是在T-3治疗的前变态蝌蚪和自然变态。特别是，在尾部，SRC 3没有以T-3依赖性方式募集到靶TR β A启动子，表明没有募集或组成型关联。最后，通过使用表达显性负SRC 3（F-dnSRC 3）的转基因蝌蚪，我们证明了F-dnSRC 3在肠道和尾部都以T-3依赖的方式募集，阻断内源性共激活因子的募集和组蛋白乙酰化。这些结果表明，SRC 3是利用在一个基因和组织特异性的方式由TR在发展过程中。
Numerous coactivators that bind nuclear hormone receptors have been isolated and characterized in vitro. Relatively few studies have addressed the developmental roles of these cofactors in vivo. By using the total dependence of amphibian metamorphosis on thyroid hormone (T-3) as a model, we have investigated the role of steroid receptor coactivator 3 (SRC3) in gene activation by thyroid hormone receptor (TR) in vivo. First, expression analysis showed that SRC3 was expressed in all tadpole organs analyzed. In addition, during natural as well as T-3-induced metamorphosis, SRC3 was up-regulated in both the tail and intestine, two organs that undergo extensive transformations during metamorphosis and the focus of the current study. We then performed chromatin immunoprecipitation assays to investigate whether SRC3 is recruited to endogenous T-3 target genes in vivo in developing tadpoles. Surprisingly, we found that SRC3 was recruited in a gene- and tissue-dependent manner to target genes by TR, both upon T-3 treatment of premetamorphic tadpoles and during natural metamorphosis. In particular, in the tail, SRC3 was not recruited in a T-3-dependent manner to the target TR beta A promoter, suggesting either no recruitment or constitutive association. Finally, by using transgenic tadpoles expressing a dominant negative SRC3 (F-dnSRC3), we demonstrated that F-dnSRC3 was recruited in a T-3-dependent manner in both the intestine and tail, blocking the recruitment of endogenous coactivators and histone acetylation. These results suggest that SRC3 is utilized in a gene- and tissue-specific manner by TR during development.