Detection of an interleukin-1 intracellular receptor antagonist mRNA variant.

At least two versions of interleukin-1 receptor antagonist generated by alternative splicing are found intracellularly, but their functions remain poorly characterized. During studies aimed at characterizing the expression of these transcripts in human articular cartilage, we detected a variant cDNA species that contained an additional 171 nucleotides within the type I interleukin-1 intracellular receptor antagonist cDNA which interrupted the coding region. This mRNA variant was also found to be expressed in keratinocytes. Translation likely initiates at an alternate methionine codon than that utilized for the previously reported interleukin-1 intracellular receptor antagonist isoforms, suggesting that this mRNA variant encodes a novel polypeptide that may play a role in interleukin-1 signaling.