Exon-Intron Organization and Sequence Comparison of Human and Murine T11 (CD2) Genes

Genomic DNA clones containing the human and murine genes coding for the 50-kDa T11 (CD2) T-cell surface glycoprotein were characterized. The human T11 gene is ≈ 12 kilobases long and comprised of five exons. A leader exon (L) contains the 5′-untranslated region and most of the nucleotides defining the signal peptide [amino acids (aa) -24 to -5]. Two exons encode the extracellular segment; exon Ex1 is 321 base pairs (bp) long and codes for four residues of the leader peptide and aa 1-103 of the mature protein, and exon Ex2 is 231 bp long and encodes aa 104-180. Exon TM is 123 bp long and codes for the single transmembrane region of the molecule (aa 181-221). Exon C is a large 765-bp exon encoding virtually the entire cytoplasmic domain (aa 222-327) and the 3′-untranslated region. The murine T11 gene has a similar organization with exon-intron boundaries essentially identical to the human gene. Substantial conservation of nucleotide sequences between species in both 5′- and 3′-gene flanking regions equivalent to that among homologous exons suggests that murine and human genes may be regulated in a similar fashion. The probable relationship of the individual T11 exons to functional and structural protein domains is discussed.