Recruitment of dioxin receptor to active transcription sites
Recruitment of dioxin receptor to active transcription sites
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DOI：
10.1091/mboc.13.6.mk0602002001
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发表时间：
2002-06-01
影响因子：
3.3
通讯作者：
Hager, GL
中科院分区：
文献类型：
--
作者：
Elbi, C;Misteli, T;Hager, GL
芳香烃受体(AhR或二恶英受体)是一种配体激活的转录因子，它与AhR核转运子(Arnt/HIF-1β)异源二聚体形成AhR/Arnt转录因子复合体。这种复合体与许多靶基因调控区域中的特定DNA位点结合，并介导外源配体的生物效应。在这里，我们用活细胞共聚焦和高分辨率去卷积显微镜研究了AhR/Arnt复合体在配体刺激下的亚细胞分布。我们发现去连接的AhR在小鼠肝癌细胞中以胞浆弥散分布为主。随着配基的增加，AhR迅速移位到细胞核，并在多个亮灶中聚集。抑制转录可阻止AhR焦点的形成。双重和三重免疫标记实验，结合新生RNA的标记，表明焦点是转录位点，表明在配体刺激下，AhR被招募到活跃的转录位点。AhR与Arnt的相互作用是AhR向转录位点募集的必要条件和充分条件。这些结果表明AhR/Arnt复合体以配体依赖的方式被招募到特定的亚核室，这些焦点代表AhR靶基因的位置。
The aryl hydrocarbon receptor (AhR or dioxin receptor) is a ligand-activated transcription factor that heterodimerizes with the AhR nuclear translocator (ARNT/HIF-1beta) to form an AhR/ARNT transcription factor complex. This complex binds to specific DNA sites in the regulatory domains of numerous target genes and mediates the biological effects of exogenous ligands. Herein, we have investigated the subcellular distribution of the AhR/ARNT complex in response to ligand stimulation, by using live-cell confocal and high-resolution deconvolution microscopy. We found that unliganded AhR shows a predominantly cytoplasmic diffuse distribution in mouse hepatoma cells. On addition of ligand, AhR rapidly translocates to the nucleus and accumulates in multiple bright foci. Inhibition of transcription prevented the formation of AhR foci. Dual- and triple-immunolabeling experiments, combined with labeling of nascent RNA, showed that the foci are transcription sites, indicating that upon ligand stimulation, AhR is recruited to active transcription sites. The interaction of AhR with ARNT was both necessary and sufficient for the recruitment of AhR to transcription sites. These results indicate that AhR/ARNT complexes are recruited to specific subnuclear compartments in a ligand-dependent manner and that these foci represent the sites of AhR target genes.