Swanson H I, Yang J H
Department of Pharmacology, University of Kentucky, Lexington, Kentucky 40536, USA.
Mol Pharmacol. 1998 Oct;54(4):671-7.
The aryl hydrocarbon receptor (AHR) and its DNA binding partner, the AHR nuclear translocator (ARNT), are basic helix-loop-helix transcription factors that mediate many of the toxic and carcinogenic effects of polyhalogenated aromatic hydrocarbons. The basic regions of the AHR and ARNT contact the GCGTG recognition site, whereas both their helix-loop-helix domains and periodicity-ARNT-single-minded domains participate in heterodimerization. To delineate the transcription factors that may facilitate DNA binding and transcriptional activation of the AHR/ARNT heterodimer, we questioned whether transcription factor IIB (TFIIB) may interact with either the AHR or ARNT and whether this interaction may affect the ability of the AHR/ARNT complex to bind DNA. Coaffinity precipitation assays demonstrated that both the AHR and ARNT were capable of interacting with TFIIB. Domain mapping experiments revealed that TFIIB interacts with the periodicity-ARNT-single-minded and carboxyl-terminal regions of the AHR. To determine whether the interaction between TFIIB and the AHR may affect DNA binding of the AHR and ARNT complex, we performed gel shift experiments in the absence and presence of TFIIB. The addition of TFIIB significantly increased the formation of the AHR/ARNT DNA binding complex, but only if TFIIB was first allowed to interact with the AHR before the addition of ARNT. These results indicate that TFIIB interacts with the AHR and may stabilize the DNA binding form of the AHR and thereby augment the ability of the AHR/ARNT complex to interact with its DNA recognition site.
芳基烃受体（AHR）及其DNA结合伴侣AHR核转运体（ARNT）是碱性螺旋-环-螺旋转录因子，介导多卤代芳烃的许多毒性和致癌作用。AHR和ARNT的碱性区域与GCGTG识别位点接触，而它们的螺旋-环-螺旋结构域和周期-ARNT-单一 minded结构域都参与异二聚化。为了确定可能促进AHR/ARNT异二聚体DNA结合和转录激活的转录因子，我们质疑转录因子IIB（TFIIB）是否可能与AHR或ARNT相互作用，以及这种相互作用是否会影响AHR/ARNT复合物结合DNA的能力。共亲和沉淀分析表明，AHR和ARNT都能够与TFIIB相互作用。结构域定位实验表明，TFIIB与AHR的周期-ARNT-单一 minded和羧基末端区域相互作用。为了确定TFIIB与AHR之间的相互作用是否会影响AHR和ARNT复合物的DNA结合，我们在有无TFIIB的情况下进行了凝胶迁移实验。添加TFIIB显著增加了AHR/ARNT DNA结合复合物的形成，但前提是在添加ARNT之前先让TFIIB与AHR相互作用。这些结果表明，TFIIB与AHR相互作用，并可能稳定AHR的DNA结合形式，从而增强AHR/ARNT复合物与其DNA识别位点相互作用的能力。
