Identification and functional characterization of two highly divergent aryl hydrocarbon receptors (AHR1 and AHR2) in the teleost Fundulus heteroclitus -: Evidence for a novel subfamily of ligand-binding basic helix loop helix-Per-ARNT-Sim (bHLH-PAS) factors
Identification and functional characterization of two highly divergent aryl hydrocarbon receptors (AHR1 and AHR2) in the teleost Fundulus heteroclitus -: Evidence for a novel subfamily of ligand-binding basic helix loop helix-Per-ARNT-Sim (bHLH-PAS) factors
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DOI：
10.1074/jbc.274.47.33814
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发表时间：
1999-11-19
影响因子：
4.8
通讯作者：
Hahn, ME
中科院分区：
文献类型：
--
作者：
Karchner, SI;Powell, WH;Hahn, ME
芳烃受体(AHR)是一种配体激活的转录因子，通过2，3，7，8-四氯二苯并对二恶英(TCDD)及其相关化合物引起基因表达改变和毒性。AKR属于一个新出现的多基因转录因子家族，具有碱性螺旋环状螺旋(BHLH)和Per-Arnt-Sim(PAS)结构域。大多数bHLH-PAS蛋白在哺乳动物中以重复或“平行对数组”的形式出现，但只有一种哺乳动物的AHR被鉴定出来。在这里，我们报道了两个不同的AHR基因的克隆，命名为FhAHR1和FhAHR2，来自单一脊椎动物--异型硬骨鱼(大西洋千里鱼)。两种Fundulus AHR蛋白都具有与哺乳动物AHR密切相关的bHLH和PAS结构域。FhAHR1和FhAHR2高度分化(总氨基酸同源性为40%，N末端同源性为61%)，表明它们起源于哺乳动物和鱼类分化之前的基因复制。用2-azido-3-[I-125]iodo-7，8-dibromodibenzo-p-dioxin进行光亲和标记和用2，3，7，8-[1，6-H-3]TCDD进行速度沉降分析表明，FhAHR1和FhAHR2都显示出与二恶英特异的高亲和力结合。这两个AHR还表现出与哺乳动物异种生物反应元件的特异性、TCDD和ARNT依赖的相互作用。这两个Fundulus AHR基因表现出不同的组织特异性表达模式；FhAHR1转录本主要在脑、心脏、卵巢和睾丸中表达，而FhAHR2转录本在许多组织中同样丰富。系统发育分析表明，Fundulus AHR1是哺乳动物AHRs的同源基因，而Fundulus和其他鱼类中的AHR2形式与Fundulus AHR1和哺乳动物AHRs相似，因此代表了一个新的脊椎动物配体结合型AHRs亚家族。
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor through which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds cause altered gene expression and toxicity. The AKR belongs to an emerging multigene family of transcription factors possessing basic helix loop helix (bHLH) and Per-ARNT-Sim (PAS) domains. Most bHLH-PAS proteins occur as duplicates or "paralog groups" in mammals, but only a single mammalian AHR has been identified. Here we report the cDNA cloning of two distinct AHRs, designated FhAHR1 and FhAHR2, from a single vertebrate species, the teleost Fundulus heteroclitus (Atlantic killifish). Both Fundulus AHR proteins possess bHLH and PAS domains that are closely related to those of the mammalian AHR. FhAHR1 and FhAHR2 are highly divergent (40% overall amino acid identity; 61% identity in the N-terminal half), suggesting that they arose from a gene duplication predating the divergence of mammals and fish. Photoaffinity labeling with 2-azido-3-[I-125]iodo-7,8-dibromodibenzo-p-dioxin and velocity sedimentation analysis using 2,3,7,8-[1,6-H-3]TCDD showed that both FhAHR1 and FhAHR2 exhibit specific, high-affinity binding of dioxins. Both AHRs also showed specific, TCDD- and ARNT-dependent interactions with a mammalian xenobiotic response element. The two Fundulus AHR genes displayed different tissue-specific patterns of expression; FhAHR1 transcripts were primarily expressed in brain, heart, ovary, and testis, while FhAHR2 transcripts were equally abundant in many tissues. Phylogenetic analysis demonstrated that Fundulus AHR1 is an ortholog of mammalian AHRs, while AHR2 forms in Fundulus and other fish are paralogous to Fundulus AHR1 and the mammalian AHRs and thus represent a novel vertebrate subfamily of ligand-binding AHRs.