Figure 1

The 5' end of the frataxin ( FXN ) gene showing the minimal promoter, exon 1 and the promoter proximal end of intron 1. TSS1 and TSS2 refer to transcription start sites described in two different studies. TSS1 was identified based on a cDNA clone isolated from cardiac mRNA [4]. TSS2 is the major start site in lymphoblastoid cells identified by primer extension [52]. The positions of various interspersed repeated sequences are indicated by the rectangles outlined with black dashed lines. The dotted black arrow indicates the estimated extent of the FXN antisense transcript-1 (FAST-1) transcript based on nested PCR [25]. The solid black line superimposed on it is the region that could be amplified by a single round of PCR. The larger antisense transcript includes an open reading frame (ORF) with a non-canonical Kozak sequence whose significance is unknown. The ORF is intact in humans but truncated in closely related primates. Arrows indicate the location of the binding sites for serum response factor (SRF), activator protein 2 (AP2) [73], CCCTC-binding factor (CTCF) [25], an early growth response protein 3 (EGR3)-like factor [73] and an E-box binding protein [48] which have been shown to be positive regulators of FXN expression.