Identification of interleukin-26 in the dromedary camel (Camelus dromedarius): Evidence of alternative splicing and isolation of novel splice variants

• Published in: Molecular immunology 2015-10, Vol.67 (2), p.357-368
• Main Authors: Premraj, Avinash, Nautiyal, Binita, Aleyas, Abi G, Rasool, Thaha Jamal
• Format: Article
• Language: English
• Subjects: Alternative splicing; Alternative Splicing - drug effects; Alternative Splicing - genetics; Amino Acid Sequence; amino acids; Animals; Camelids; Camelpox virus; camels; Camelus - genetics; Camelus dromedarius; Cloning, Molecular; complementary DNA; Cytokine; DNA, Complementary - genetics; exons; Exons - genetics; Female; fibroblasts; Fibroblasts - drug effects; Fibroblasts - metabolism; Fibroblasts - virology; Gene Expression Profiling; horses; IL-10; IL-26; interleukin-10; Interleukins - genetics; Interleukins - metabolism; Introns - genetics; kidneys; Leukocytes, Mononuclear - drug effects; Leukocytes, Mononuclear - metabolism; liver; lymph nodes; messenger RNA; mice; Mitogens - pharmacology; Molecular Sequence Data; mononuclear leukocytes; nucleotides; open reading frames; Orthopoxvirus; Ovary - pathology; Phylogeny; Poxviridae Infections - genetics; Poxviridae Infections - pathology; Poxviridae Infections - virology; Protein Isoforms - genetics; Protein Isoforms - metabolism; proteins; rats; RNA, Messenger - genetics; RNA, Messenger - metabolism; Sequence Alignment; sequence analysis; signal peptide; stop codon; Structural Homology, Protein; Virus
• ISSN: 0161-5890; 1872-9142
• DOI: 10.1016/j.molimm.2015.06.022

•Identified and cloned IL-26 cDNA from the dromedary camel.•First report of alternative splicing of IL-26 in species where the gene is not inactivated.•Identified novel IL-26 splice variants generated by alternative splicing at the exon 3- exon 4 region.•IL-26 Tv2 expression seems to be induced in camel fibroblast cells infected with Camel pox virus. Interleukin-26 (IL-26) is a member of the IL-10 family of cytokines. Though conserved across vertebrates, the IL-26 gene is functionally inactivated in a few mammals like rat, mouse and horse. We report here the identification, isolation and cloning of the cDNA of IL-26 from the dromedary camel. The camel cDNA contains a 516bp open reading frame encoding a 171 amino acid precursor protein, including a 21 amino acid signal peptide. Sequence analysis revealed high similarity with other mammalian IL-26 homologs and the conservation of IL-10 cytokine family domain structure including key amino acid residues. We also report the identification and cloning of four novel transcript variants produced by alternative splicing at the Exon 3-Exon 4 regions of the gene. Three of the alternative splice variants had premature termination codons and are predicted to code for truncated proteins. The transcript variant 4 (Tv4) having an insertion of an extra 120bp nucleotides in the ORF was predicted to encode a full length protein product with 40 extra amino acid residues. The mRNA transcripts of all the variants were identified in lymph node, where as fewer variants were observed in other tissues like blood, liver and kidney. The expression of Tv2 and Tv3 were found to be up regulated in mitogen induced camel peripheral blood mononuclear cells. IL-26-Tv2 expression was also induced in camel fibroblast cells infected with Camel pox virus in-vitro. The identification of the transcript variants of IL-26 from the dromedary camel is the first report of alternative splicing for IL-26 in a species in which the gene has not been inactivated.