Genomic organization and chromosomal location of the human gene encoding the B-lymphocyte activation antigen B7.
The human B lymphocyte activation antigen B7 provides regulatory signals for T lymphocytes as a consequence of binding to its ligands CD28 and CTLA-4. The cDNA for B7 has previously been isolated and predicted to encode a type I membrane protein. The predicted polypeptide has a secretory signal peptide followed by two contiguous Ig-like domains, a hydrophobic transmembrane region and a short cytoplasmic tail. Here we report the exon-intron genomic organization of human B7 and the chromosomal location. The gene has six exons that span approximately 32 kilobases of DNA. Exon 1 is not translated and the second exon contains the initiation ATG codon and encodes a predicted signal peptide. This gene structure is characteristic for several eukaryotic genes with tissue-specific expression. The third and fourth exons correspond to two Ig-like domains whereas the fifth and sixth exons encode respectively the trans-membrane portion and the cytoplasmic tail. This close relationship between exons and functional domains is a characteristic feature of genes of the Ig superfamily. Cell surface expression of the B7 gene product has previously been mapped to human chromosome 12 by antibody reactivity with the B7-specific monoclonal antibody BB-1. We here demonstrate that the B7 gene is located to the q21-qter region of chromosome 3 by DNA blot analysis of human x rodent somatic cell hybrids.
Selvakumar
A
A
Human Immunogenetics Laboratory, Sloan-Kettering Institute for Cancer Research, New York, NY 10021.
Mohanraj
B K
BK
Eddy
R L
RL
Shows
T B
TB
White
P C
PC
Dupont
B
B
D000595:Amino Acid Sequence; D000954:Antigens, Surface / Q000235:genetics*; D018122:B7-1 Antigen; D001483:Base Sequence; D002893:Chromosomes, Human, Pair 3; D005796:Genes; D006801:Humans; D008969:Molecular Sequence Data; D015183:Restriction Mapping
D000954:Antigens, Surface; D018122:B7-1 Antigen