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FR-α gene organization. The 7.5-kb FR-α gene structure is shown with seven exons (labeled 1 to 7) and six introns (labeled A to F). The two promoters, P1 and P4, are shown in shaded boxes. The P1 promoter occurs upstream of exon 1, and the P4 promoter occurs upstream of exon 4. The arrows at the left and right sides indicate nucleotide positions; the transcription start site for the P4 promoter is labeled +1.
