Genomic organization of the human leukocyte immunoglobulin-like receptors within the leukocyte receptor complex on Chromosome 19q13.4

The leukocyte immunoglobulin (Ig)-like receptors (LIRs) comprise a family o f eel surface receptors that couple to either activating or inhibitory sign als depending on the nature of their transmembrane and cytoplasmic domains. We describe the organization and fine localization of the genes for LIR-1 and LIR-5, which are inhibitory receptors, and LIR-6, which is an activatin g receptor. The genomic organization of all three genes is highly conserved from the signal peptide through the membrane-proximal Ig domain but diverg es thereafter depending on the inhibitory or activating nature of the gene product. The 3' untranslated region of the gene for LIR-6 contains a 37-bas e pair repeat not present in the LIR-1 or LIR-5 genes. 5' rapid amplificati on of cDNA ends defined the putative transcription initiation site of the L IR-5 gene, which is TATA-less. A nucleotide substitution in the LIR-5 gene led to loss of an intron present in the 5' untranslated region of the LIR-1 and LIR-6 genes. Differences in the genomic structure of these three LIR g enes suggests possible mechanisms for their differential expression in cell s of hematopoietic lineage. The three genes are in a region of Chromosome 1 9q13.4 that is immediately centromeric of the killer cell Ig-like receptor genes and are separated from one another by similar to 20 to 30 kb, suggest ing that they arose by gene duplication from a common ancestor.