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The TCDD-dependent ERα-WT recruitment to CYP1A1 and CYP1B1 detected in ChIP assays correlated well with increases in CYP1A1- and CYP1B1-regulated reporter gene activity and endogenous CYP1A1 and CYP1B1 mRNA expression. Despite observing substantial TCDD-induced recruitment of ERα-ΔAF1 to CYP1A1 and CYP1B1, significant increases in AHR-mediated reporter gene activity or TCDD-induced CYP1A1 or CYP1B1 mRNA JNJ-26481585 levels were not observed. In contrast, no significant TCDD-induced recruitment of ERα-AF2mut to CYP1A1 or CYP1B1 regulatory regions, or increases in AHR-mediated reporter gene activity or TCDD-induced CYP1A1 or CYP1B1 mRNA expression levels was detected. Collectively these observations suggest the AF2 domain is required for TCDD-dependent recruitment of ERα to AHR targets, whereas the AF1 domain is important for mediating the ERα enhancement of AHR target gene expression.
In summary, we identified the AF2 region of ERα as an important regulator of the TCDD-induced recruitment of ERα to AHR-regulated genes, and that the AF1 domain is important in mediating the ERα-dependent increase in AHR activity in HuH-7 cells. Our data demonstrate that activation of AHR in cells that also express ERα will result in the co-recruitment of ERα to some AHR regulated genes.