Exon/intron organization of the genes coding for the δ chains of the human and murine T-cell receptor/T3 complex

Abstract

Genomic DNA clones containing the gene coding for the 20-kDa T3 glycoprotein of the T-cell receptor/T3 complex (T3-δ chain) of human and mouse were isolated and characterized. The human T3-δ gene is ~ 4 kilobases (kb) long and contains five exons: a 151-base-pair (bp) exon containing the 5' untranslated and the coding sequences of the signal peptide, one exon of 219 bp, which contains most of the extracellular segment of the T3-δ chain, one 130-bp-long exon coding mainly for the transmembrane portion of the molecule, and two exons of 44 bp and 156 bp encoding the cytoplasmic domain and 3' untranslated region of the T3-δ chain, respectively. The murine T3-δ gene, which has a similar organization, contains 5 kb, because the first intron is ~ 1 kb larger than in the human gene. Two major mRNA initiation sites within a small area ~ 100 nucleotides 5' of the AUG codon were determined by S2 nuclease analysis and primer-extension studies. The remarkably high level of conservation of nucleotide sequences in this region suggests that this segment may be important for the regulation of T-cell-specific transcription of the T3-δ gene. The T3-δ gene does not contain the 'TATA box' found in many eukaryotic promoters.