Development of novel assay system based on nuclear receptor function

类固醇激素通过同源核受体发挥作用，这些受体作用于配体诱导的转录因子。对于这种配体诱导的反式激活，配体结合核受体，核受体依赖于配体结合，但它只被激动剂诱导，而不是拮抗剂。本研究利用生物化学方法和酵母双杂交系统寻找雌激素、雄激素、盐皮质激素、维生素D核受体的新辅激活因子，并筛选出几个候选cDNA。特别是，我们发现TGF-β信号诱导剂Smad 3是VDR的共激活剂，并建立了一个基于共激活剂与酵母核受体相互作用的检测系统，以评价相关化合物的激动/拮抗活性。

Steroid hormones exert their actons through cognate nuclear receptors, which act ligand-inducible transcriptional factors. For this ligand-induced transactivation, ligand-bound nuclear receptors, nuclear receptors depend on ligand binding, but it Is induced only by agonist, but not antgonist. In the present study, we searched novel coactivators for nuclear receptors for estrogen, androgen mineralcorticoid, vitamin D by biochemical approaches and yeast two-hybrid systen, and found several candidate cDNAs. Especially, we found that Smad3, TGF-beta signal inducers, acts as coactivator for VDR.Moreover, we developed an assay system based on the interactions of coactivators with nuclear receptors in yeast to evaluate agonistic/antagonistid activity of related compounds.