FIGURE 2.

FXN transcription start site in lymphoblastoid cells. Left panel, sequencing gel showing the product of primer extension with end-labeled Exon 1 R2 primer and RNA from unaffected (UN) and FRDA cells using SuperScript III reverse transcriptase according to standard procedures. G, A, T, and C lanes represent the sequencing reactions from the corresponding region of DNA in plasmid FXN81658 (4) using the same primer. MW, pBR322 DNA digested with MspI. Right panel, DNA sequence of the 5′ end of the FXN locus showing the position of previously reported transcription start site, TSS1 (15), and the transcription start site TSS2 identified in this study. The numbers alongside the sequence indicate the position of bases with respect to the first base of the open reading frame, which is shown in the open box. The sequence between the two brackets is the sequence −221 to −121 bases upstream of the frataxin open reading frame, which we showed previously to be important for FXN promoter activity in muscle cells (32). The region highlighted in gray corresponds to the remnants of an ancient L2 repeated DNA element.