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Protein-DNA interactions at recognition sites for the dioxin-Ah receptor complex
M S Denison1, J M Fisher, J P Whitlock
1Department of Pharmacology, Stanford University School of Medicine, California 94305.
The Journal of Biological Chemistry
|October 5, 1989
Summary
Researchers identified six binding sites for the liganded Ah receptor near the mouse CYP1A1 gene, defining a specific DNA recognition motif. This finding highlights differences in how dioxins and steroid hormones interact with DNA.
Area of Science:
- Molecular biology
- Genetics
- Biochemistry
Background:
- The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor.
- Understanding AhR binding to DNA is crucial for deciphering gene regulation by environmental pollutants like dioxins.
Purpose of the Study:
- To identify and characterize the DNA binding sites for the liganded Ah receptor upstream of the mouse CYP1A1 gene.
- To determine the consensus DNA sequence recognized by the liganded Ah receptor.
Main Methods:
- Gel retardation assays were used to detect receptor-DNA interactions.
- DNA sequencing and motif analysis were employed to define the recognition site.
Main Results:
- A cluster of six Ah receptor binding sites was found within a 700-bp region upstream of the mouse CYP1A1 gene.
- A non-symmetric consensus recognition motif was defined for the liganded Ah receptor.
- Receptor-DNA interaction decreased upon alteration of the consensus motif, indicating its importance.
- The liganded Ah receptor binds as a monomer and preferentially to double-stranded DNA.
Conclusions:
- The study defines the specific DNA sequence and binding characteristics of the liganded Ah receptor.
- These findings reveal distinct mechanisms of action between 2,3,7,8-tetrachlorodibenzo-p-dioxin and steroid hormones in gene regulation.