Speckled 100 kDa (Sp100) plays an important role in the antiviral immune response, however, little is known about porcine Sp100. In this study, porcine Sp100 was cloned and its response to interferon (IFN) α was identified. We obtained the cDNA (V1) of the gene, SP100, and seven alternative splicing variants (V2-8). Isoform V1 encoded a 386 amino acid protein and contained a homogeneously-staining region (HSR) domain. Isoforms V3, 4, 6 and 7 were deletion/insertion variants and contained HSR domain as V1. The splicing of porcine SP100 was very complicated and many transcripts existed as revealed by cloning and minigene analyses. Using GFP-fusion constructs isoforms V1, 3, 4, 6 and 7 were localized to nucleus and the nuclear localization signal was identified as PSNRKRR at positions 331-337 of V1. Porcine SP100 was unevenly distributed in all tissues studied and differentially expressed between pigs with different disease-resistance/susceptibilities. Porcine SP100 was strongly increased by IFNα due to the existence of an IFN-stimulated response element in the promoter. A single nucleotide - 70A > C polymorphism enhanced promoter activity. The results provided the basis for determining the role of Sp100 in antiviral responses and may assist in breeding pigs with high disease-resistance.
Keywords: IFN-stimulated response element; Polymorphism; Promoter; SP100; Transcript variant.
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