Genomic sequence for human prointerleukin 1 beta: possible evolution from a reverse transcribed prointerleukin 1 alpha gene.

We have isolated the human prointerleukin 1 (proIL-1) beta gene from leukocyte and fetal liver libraries. The nucleotide sequence and its gene organization reveals that the proIL-1 beta gene is composed of seven exons with a primary transcription product length of 7,008 nucleotides. The exon sequence agrees well with that of the human proIL-1 beta cDNA. Features of interest within the transcriptional unit include positioned TATA, CAT, and poly-adenylation signals for gene regulation, as well as the signatures of gene duplication via retrotransposition in the form of flanking direct repeats and a genomic poly A tail. The genomic organization of the proIL-1 beta gene with respect to the number and position of exon boundaries is strikingly similar to that of the recently reported human proIL-1 alpha gene. Therefore, we hypothesize that the proIL-1 beta may have arisen by a reverse transcriptase mediated duplication of the related alpha gene.