Figure 4.

ChIP assay showing that the ABCG2 promoter was enriched with AhR in romidepsin- or B(a)P-treated responsive cell lines. A, a schematic representation of the ABCG2 promoter studied by ChIP analysis. Two sets of primers were used for amplification of the proximal (P3) and distal ABCG2 promoter. Nucleotide positions are numbered relative to the major transcription start site (+1) defined in the published DNA sequence (Genbank accession no. AF151530). Big arrowhead, transcription start site. B, ChIP analyses targeting the proximal and distal region of the ABCG2 promoter in romidepsin or B(a)P-treated cells (4 hours), using antibody against AhR. Input, DNA isolated from the lysate before immunoprecipitation (only 10% of the total chromatin was used for the PCR reactions and it was run as the “input” in the gel electrophoresis); IgG, ChIP using normal IgG for immunoprecipitation. A representative set of result from 3 independent immunoprecipitations is shown.