Estrogen-related receptor (ERR), a member of the nuclear receptor superfamily, consists of three subtypes (α, β, γ) and has strong homology with estrogen receptor. No endogenous ligands have been identified for ERRs, but they play key roles in metabolic, hormonal, and developmental processes as transcription factors without ligand binding. Although subnuclear dynamics are essential for nuclear events including nuclear receptor-mediated transcriptional regulation, the dynamics of ERRs are poorly understood. Here, we report that ERRs show subcellular kinetic changes in response to diethylstilbestrol (DES), a synthetic estrogen that represses the transactivity of all three ERR subtypes, using live-cell imaging with fluorescent protein labeling. Upon DES treatment, all ERR subtypes formed discrete clusters in the nucleus, with ERRγ also displaying nuclear export. Fluorescence recovery after photobleaching analyses revealed significant reductions in the intranuclear mobility of DES-bound ERRα and ERRβ, and a slight reduction in the intranuclear mobility of DES-bound ERRγ. After DES treatment, colocalization of all ERR subtypes with scaffold attachment factor B1 (SAFB1), a nuclear matrix-associated protein, was observed in dot-like subnuclear clusters, suggesting interactions of the ERRs with the nuclear matrix. Consistently, co-immunoprecipitation analyses confirmed enhanced interactions between ERRs and SAFB1 in the presence of DES. SAFB1 was clarified to repress the transactivity of all ERR subtypes through the ERR-response element. These results demonstrate ligand-dependent cluster formation of ERRs in the nucleus that is closely associated with SAFB1-mediated transrepression. Taken together, the present findings provide a new understanding of the pathophysiology regulated by ERR/SAFB1 signaling pathways and their subcellular dynamics.

雌激素相关受体（Estrogen-related receptor，ERR）是核受体超家族的一员，由三个亚型（α、β、γ）组成，与雌激素受体有很强的同源性。尚未鉴定出 ERR 的内源性配体，但它们作为没有配体结合的转录因子在代谢、激素和发育过程中发挥着关键作用。尽管亚核动力学对于包括核受体介导的转录调控在内的核事件至关重要，但人们对 ERR 的动力学知之甚少。在这里，我们报告说 ERR 显示出响应己烯雌酚 (DES) 的亚细胞动力学变化，DES 是一种合成雌激素，使用带有荧光蛋白标记的活细胞成像来抑制所有三种 ERR 亚型的反式活动。DES 治疗后，所有 ERR 亚型在细胞核中形成离散的簇，ERRγ 也显示核输出。光漂白分析后的荧光恢复显示，结合 DES 的 ERRα 和 ERRβ 的核内迁移率显着降低，结合 DES 的 ERRγ 的核内迁移率略有降低。DES 治疗后，在点状亚核簇中观察到所有 ERR 亚型与支架附着因子 B1（SAFB1）（一种核基质相关蛋白）共定位，表明 ERR 与核基质相互作用。一致地，共免疫沉淀分析证实了在存在 DES 的情况下 ERR 和 SAFB1 之间的相互作用增强。SAFB1 被阐明通过 ERR 响应元件抑制所有 ERR 亚型的交易性。这些结果表明，细胞核中 ERR 的配体依赖性簇形成与 SAFB1 介导的反式抑制密切相关。总之，本研究结果提供了对 ERR/SAFB1 信号通路及其亚细胞动力学调节的病理生理学的新理解。