Cloning and chromosome mapping of the human interleukin-1 receptor antagonist gene

By screening a human genomic library with an interleukin-1 receptor antagonist (IL-1ra) cDNA probe, we have isolated a 15 kb clone which contains the entire coding region of the gene as expressed in monocytes, and includes 6 kb of 5'-upstream sequence. The gene contains four exons which code for the secreted form of the IL-1ra, however, our clone does not contain the alternative first exon used to generate an intracellular form of the protein as the protein as found in epithelial cells. Analysis of the sequence reveals a consensus TATA box, and three Alu repeats, two of which are in the upstream region and one in intron 3. The sequence also reveals an 86 bp motif tandomly repeated four times within intron 2, and may reflect the polymorphism known to exist in this region of the gene. By in-situ fluorescence hybridization we have shown that the IL-1ra gene is found on the long arm of chromosome 2 and maps to 2q13-14.1. Previous studies have revealed that IL-1 alpha, and IL-1 beta and both type I and type II forms of the IL-1 receptor all map close to this region of chromosome 2.