共平面的3,3',4,4',5-五氯联苯和非共平面的2,2',4,6,6'-五氯联苯对雌激素受体α募集至芳烃受体靶基因的诱导作用存在差异。
Co-planar 3,3',4,4',5-pentachlorinated biphenyl and non-co-planar 2,2',4,6,6'-pentachlorinated biphenyl differentially induce recruitment of oestrogen receptor alpha to aryl hydrocarbon receptor target genes.
作者信息
Matthews Jason, Wihlén Björn, Heldring Nina, MacPherson Laura, Helguero Luisa, Treuter Eckardt, Haldosén Lars-Arne, Gustafsson Jan-Ake
机构信息
Department of Pharmacology, University of Toronto, Rm 4336, Medical Sciences Building, 1 King's College Circle, Toronto, ON, Canada M5S 1A8.
出版信息
Biochem J. 2007 Sep 1;406(2):343-53. doi: 10.1042/BJ20070585.
In the present study we examined the ability of 3,3',4,4',5-pentachlorinated biphenyl [PCB126 (polychlorinated biphenyl 126)], a prototypical AHR (aryl hydrocarbon receptor) agonist, and 2,2',4,6,6'-PCB (PCB104), which does not activate AHR, to induce the recruitment of ERalpha (oestrogen receptor alpha) to CYP1A1 (cytochrome P4501A1 gene) and CYP1B1 promoters in T-47D human breast cancer cells and other cell lines. PCB126 treatment strongly induced CYP1A1 and CYP1B1 mRNA expression that was unaffected by co-treatment with E2 (17beta-oestradiol). PCB104 failed to induce changes in either CYP1A1 or CYP1B1 expression levels. ChIP (chromatin immunoprecipitation) assays show that PCB126, but not PCB104, increased the promoter occupancy by ERalpha to CYP1A1 and CYP1B1 promoters. Co-treatment with PCB126+E2 significantly enhanced the promoter occupancy of ERalpha at CYP1A1, whereas co-treatment with PCB126+4-hydroxytamoxifen or ICI182,780 did not. Competitive binding studies revealed that neither PCB126 nor PCB104 bound to ERalpha. HEK-293 cells (human embryonic kidney-293 cells) stably transfected with ERalpha showed significantly higher PCB126-induced CYP1A1 expression compared with empty vector controls, whereas no increase was observed in cells stably transfected with ERalpha lacking its N-terminal AF1 (activation function-1) domain (ERalphaDeltaAF1). Despite no increase in AHR-mediated gene expression, ChIP assays revealed that ERalphaDeltaAF1 was present at CYP1A1 and CYP1B1 promoters. HC11 mouse mammary cells stably expressing shRNA (small-hairpin RNA) against ERalpha showed an 8-fold reduction in PCB126-dependent Cyp1a1 expression. Our results provide further evidence that AHR agonists induce ERalpha promoter occupancy at AHR target genes through indirect activation of ERalpha, and support a role for ERalpha in AHR transactivation.
在本研究中，我们检测了典型的芳烃受体（AHR）激动剂3,3',4,4',5-五氯联苯[多氯联苯126（PCB126）]以及不激活AHR的2,2',4,6,6'-多氯联苯（PCB104）在T-47D人乳腺癌细胞和其他细胞系中诱导雌激素受体α（ERα）募集至细胞色素P450 1A1（CYP1A1基因）和CYP1B1启动子的能力。PCB126处理强烈诱导CYP1A1和CYP1B1 mRNA表达，而与17β-雌二醇（E2）共处理对此无影响。PCB104未能诱导CYP1A1或CYP1B1表达水平发生变化。染色质免疫沉淀（ChIP）分析表明，PCB126而非PCB104增加了ERα对CYP1A1和CYP1B1启动子的启动子占有率。PCB126与E2共处理显著增强了ERα在CYP1A1启动子的占有率，但PCB126与4-羟基他莫昔芬或ICI182,780共处理则未出现这种情况。竞争性结合研究表明，PCB126和PCB104均不与ERα结合。与空载体对照相比，稳定转染ERα的人胚肾-293（HEK-293）细胞中PCB126诱导的CYP1A1表达显著更高，而在稳定转染缺失其N端激活功能-1（AF1）结构域的ERα（ERαDeltaAF1）的细胞中未观察到增加。尽管AHR介导的基因表达未增加，但ChIP分析表明ERαDeltaAF1存在于CYP1A1和CYP1B1启动子处。稳定表达针对ERα的短发夹RNA（shRNA）的HC11小鼠乳腺细胞中PCB126依赖性Cyp1a1表达降低了8倍。我们的结果提供了进一步的证据表明AHR激动剂通过间接激活ERα诱导ERα在AHR靶基因处的启动子占有率，并支持ERα在AHR反式激活中的作用。
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