Single Nucleotide Polymorphisms (SNPs) Distant from Xenobiotic Response Elements Can Modulate Aryl Hydrocarbon...

Area of Science:

• Pharmacogenomics
• Molecular toxicology
• Gene regulation

Background:

• CYP1A1 expression is regulated by the aryl hydrocarbon receptor (AHR).
• Single-nucleotide polymorphisms (SNPs) near regulatory elements may influence gene expression.
• The impact of SNPs distant from xenobiotic response elements (XREs) on AHR binding is not well understood.

Purpose of the Study:

• To investigate if SNPs located hundreds of base pairs (bp) from XREs affect AHR binding and CYP1A1 gene expression.
• To analyze the role of the rs2470893 SNP in the CYP1A1 promoter in mediating AHR-XRE interactions and gene expression.
• To explore potential mechanisms of distant SNP effects on AHR-mediated gene regulation.

Main Methods:

• Analysis of DNA sequences flanking CYP1A1 for putative XREs and nearby SNPs.
• Utilized a human lymphoblastoid cell line (LCL) model system.
• Measured CYP1A1 mRNA levels after 3-methylcholanthrene (3MC) treatment.
• Performed electrophoretic mobility shift assays (EMSA) and mass spectrometry to assess AHR binding and protein interactions.

Main Results:

• The rs2470893 SNP (-1694G>A), located 196 bp from a CYP1A1 promoter XRE, significantly influenced AHR-XRE binding.
• LCLs with the AA genotype showed 2-fold higher AHR-XRE binding and CYP1A1 mRNA expression after 3MC treatment compared to the GG genotype.
• EMSA and mass spectrometry confirmed SNP-dependent AHR binding and identified candidate proteins interacting with AHR.

Conclusions:

• The rs2470893 SNP is associated with variations in 3MC-dependent AHR binding and CYP1A1 expression.
• Demonstrated a
• distant SNP effect
• on AHR binding to a CYP1A1 promoter XRE.
• Suggests that similar mechanisms may regulate other AHR-target genes.