Restriction map, organization and transcripts of the LU gene. (A) Restriction map and organization of the LU gene. The organization of the LU gene was established from analysis of the λ Lub1.2 and λ Lub3.1 genomic clones. Exons 1 to 15 are numbered and represented by open boxes. The hatched box indicates the alternative spliced intron and the interrupted black boxes represent the two l DASH arms. (B) Schematic representation of the alternative splicing of intron 13. Alternative splicing of intron 13 results in the synthesis of two transcripts of 2.5 kb and 4.0 kb encoding the long-tail (85 kD) and the short-tail (78 kD) Lu polypeptides, respectively. The exons are represented by open boxes. The hatched box indicates the alternative spliced intron.