Unique functional properties of a member of the Fushi Tarazu-Factor 1 family from Schistosoma mansoni
Unique functional properties of a member of the Fushi Tarazu-Factor 1 family from Schistosoma mansoni
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DOI：
10.1042/bj20040489
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发表时间：
2004-08-15
影响因子：
4.1
通讯作者：
Pierce, RJ
中科院分区：
文献类型：
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作者：
Bertin, B;Sasorith, S;Pierce, RJ
SmFtz-F1(Schistosoma mansoni Fushi Tarazu-factor1)属于核受体FTZ-F1亚家族，但与其哺乳动物同源物SF-1(类固醇生成因子-1)或肝脏受体同源物-1在结构上存在显著差异。它们包括一个长的F结构域(104个氨基酸)，一个异常大的铰链区(133个氨基酸)和一个保守程度较低的E结构域。在这里，使用Gal4结构和哺乳动物双杂交实验，我们已经表征了这些特定区域在受体转录活性及其与辅因子相互作用中的作用。我们的结果表明，尽管AF-2(激活功能-2)区是该受体的主要激活功能，但F和D结构域对于AF-2依赖的活性是必不可少的。SmFtz-F1 LBD(配体结合结构域)的建模和结构导向突变使我们能够显示螺旋H1在维持LBD结构构象方面的重要作用，并表明其自主反式激活活性，也与SF-1一起观察到，是偶然的。这一策略也使我们能够研究这个孤儿受体的最终配体依赖性，预测的三维模型表明，SmFtz-F1 LBD包含一个大的和定义明确的配体结合口袋，由两个精氨酸残基密封，定向到腔的内部。这两个残基的突变导致SmFtz-F1受体转录活性的丧失，并强烈减少其与类固醇受体辅因子-1(SRC1)的相互作用，表明SmFtz-F1的活性依赖于配体。综上所述，我们的结果证明了这种扁形线虫核受体具有独特的功能活性。
SmFtz-F1 (Schistosoma mansoni Fushi Tarazu-Factor 1) belongs to the Ftz-F1 subfamily of nuclear receptors, but displays marked structural differences compared with its mammalian homologues SF-1 (steroidogenic factor-1) or liver receptor homologue-1. These include a long F domain (104 amino acids), an unusually large hinge region (133 amino acids) and a poorly conserved E-domain. Here, using Gal4 constructs and a mammalian two-hybrid assay, we have characterized the roles of these specific regions both in the transcriptional activity of the receptor and in its interactions with cofactors. Our results have shown that, although the AF-2 (activation function-2) region is the major activation function of the receptor, both the F and D domains are essential for AF-2-dependent activity. Modelling of SmFtz-F1 LBD (ligand-binding domain) and structure-guided mutagenesis allowed us to show the important role of helix H1 in maintaining the structural conformation of the LBD, and suggested that its autonomous transactivation activity, also observed with SF-1, is fortuitous. This strategy also allowed us to study an eventual ligand dependence for this orphan receptor, the predicted three-dimensional models suggesting that the SmFtz-F1 LBD contains a large and well-defined ligand-binding pocket sealed by two arginine residues orientated towards the interior of the cavity. Mutation of these two residues provoked a loss of transcriptional activity of the receptor, and strongly reduced its interaction with SRC1 (steroid receptor cofactor-1), suggesting a ligand-dependent activity for SmFtz-F1. Taken together, our results argue for original and specific functional activities for this platyhelminth nuclear receptor.