Fig. 1.

Exon 1 of β3Gal-T5 is derived from an endogenous retroviral LTR. Exon (E) sequences are shown in uppercase reverse type, with all other sequences in lowercase. The translation initiation codon at the beginning of exon 4 and the 5-bp direct repeats flanking the LTR are shown in italics. The ERV-L LTR sequence is shown in bold and framed with a solid black line. Dotted white lines frame the portion of exon 1 included in splicing variant 1, but not variant 2; three minor splicing variants, which contain additional exon sequences, are not shown (see ref. 15). Gray boxes, putative HNF-1 binding sites; underlined text, putative CCAAT box; dashed underlined text, putative Jun binding site; unfilled boxes, putative Sp1 binding sites.