Cloning of equine interleukin 1 receptor antagonist and determination of its full-length cDNA sequence

Abstract

Objectives: To clone equine interleukin 1 receptor antagonist (IL-1ra) and determine its full-length cDNA sequence.

Procedure: A cDNA library derived from lipopolysaccharide-stimulated equine monocytes was screened by means of plaque hybridization to radiolabeled equine IL-1ra DNA probes generated by means of the polymerase chain reaction. The cDNA nucleotide sequence for equine IL-1ra was determined by use of the dideoxy chain termination technique, analyzed by use of computer software for sequence characteristics, and compared with sequences reported for IL-1ra of other species.

Results: The cDNA of equine IL-1ra was 1,614 base pairs in length with an ORF encoding a peptide of 177 amino acids with a predicted molecular mass of 20.427 kd. Similarity between the amino acid sequence of equine IL-1ra and sequences for human, murine, rat, and lapine IL-1ra was 76%. Similarity between sequence for equine IL-1ra and sequences for equine interleukin-1 alpha and equine interleukin-1 beta were 22.6 and 24.6%, respectively.

Conclusion: Comparison of the sequence for equine IL-1ra with sequences for IL-1ra of other species indicated a high degree of conservation.

Clinical relevance: Results establish a basis for studying the roles of interleukin-1 in healthy and diseased joints in horses.