Re: IBD & Dioxins Link?

> Dioxin: a review of its environmental effects and its aryl hydrocarbon
> receptor biology...

The Aryl Hydrocarbon Receptor complex and the control of gene
expression.
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 TCDD 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 im****tant mode of regulation. Inflammatory signaling pathways
and the AhR also appear to be another im****tant 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. PMID: 18540824