Configuration of A) human SHBG exon 1L and B) exon 1T. Transcriptional start sites, as determined in this study, are in bold letters and are denoted by a "≥ ". For both exons, position +1 is assigned to the distal, upstream start site. The exon 1L proximal start site is at position +42, the exon 1T proximal start site is at position +23. Upstream sequences are in italics. Previously reported human transcriptional start sites are underlined; not shown are two additional exon 1L start sites mapped at positions -114 and -125 . Transcriptional start sites mapped in transgenic mice are in lower case letters . "r" and "b" denote the corresponding positions of the major exon 1L rat  and rabbit  transcriptional start sites, respectively.