Schematic representations of protein 4.1 (A), cDNA (B), primers (C), and cDNA probes (D). (A) Structural domains of the erythroid protein 4.1, derived from limited chymotryptic cleavage. (B) (▩) Constitutive coding sequences; (▧) alternative coding sequences; (░) the 5′ end of exon 2 and exon 16 are the only motifs where alternative splicing is endowed with known physiological significance; (▦) alternative noncoding sequence; (□) untranslated regions. ATG* and ATG** indicate upstream and downstream translation initiation codons, respectively. (C) Schematic representation of the primers used in 5′ RACE experiments (see also Table 1). (D) Schematic localization of the cDNA and genomic DNA probes used in Southern blot analysis. Probes encompassing exonic (thick bar) and intronic (thin bar) regions.