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Critical Reviews™ in Eukaryotic Gene Expression

Impact factor: 2.385

ISSN Print: 1045-4403
ISSN Online: 2162-6502

Critical Reviews™ in Eukaryotic Gene Expression

DOI: 10.1615/CritRevEukarGeneExpr.v18.i3.20
pages 207-250

The Aryl Hydrocarbon Receptor Complex and the Control of Gene Expression

Timothy V. Beischlag
Center for Molecular Toxicology and Carcinogenesis and the Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA
J. Luis Morales
Center for Molecular Toxicology and Carcinogenesis and the Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA
Brett D. Hollingshead
Center for Molecular Toxicology and Carcinogenesis and the Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA
Gary H. Perdew
Center for Molecular Toxicology and Carcinogenesis and the Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA

ABSTRACT

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that controls the expression of a diverse set of genes. The toxicity of the potent AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin is almost exclusively mediated through this receptor. However, the key alterations in gene expression that mediate toxicity are poorly understood. It has been established through characterization of AhR-null mice that the AhR has a required physiological function, yet how endogenous mediators regulate this orphan receptor remains to be established. A picture as to how the AhR/ARNT heterodimer actually mediates gene transcription is starting to emerge. The AhR/ARNT complex can alter transcription both by binding to its cognate response element and through tethering to other transcription factors. In addition, many of the coregulatory proteins necessary for AhR-mediated transcription have been identified. Cross talk between the estrogen receptor and the AhR at the promoter of target genes appears to be an important mode of regulation. Inflammatory signaling pathways and the AhR also appear to be another important site of cross talk at the level of transcription. A major focus of this review is to highlight experimental efforts to characterize nonclassical mechanisms of AhR-mediated modulation of gene transcription.