Interferon-induced proteins with tetratricopeptide repeats (IFITs) are involved in antiviral defense. Members of this protein family contain distinctive multiple structural motifs comprising tetratricopeptides that are tandemly arrayed or dispersed along the polypeptide. IFIT-encoding genes are upregulated by type I interferons (IFNs) and other stimuli. IFIT proteins inhibit virus replication by binding to and regulating the functions of cellular and viral RNA and proteins. In teleost fish, knowledge about genes and functions of IFITs is currently limited. In the present work, we describe an IFIT5 orthologue in Atlantic salmon (SsaIFIT5) with characteristic tetratricopeptide repeat motifs. We show here that the gene encoding SsaIFIT5 (SsaIfit5) was ubiquitously expressed in various salmon tissues, while bacterial and viral challenge of live fish and in vitro stimulation of cells with recombinant IFNs and pathogen mimics triggered its transcription. The profound expression in response to various immune stimulation could be ascribed to the identified IFN response elements and binding sites for various immune-relevant transcription factors in the putative promoter of the SsaIfit5 gene. Our results establish SsaIfit5 as an IFN-stimulated gene in A. salmon and strongly suggest a phylogenetically conserved role of the IFIT5 protein in antimicrobial responses in vertebrates.

具有四三肽重复序列的干扰素诱导蛋白 (IFIT) 参与抗病毒防御。该蛋白质家族的成员包含独特的多重结构基序，包括沿多肽串联排列或分散的四三肽。IFIT 编码基因被 I 型干扰素 (IFN) 和其他刺激物上调。IFIT 蛋白通过结合并调节细胞和病毒 RNA 和蛋白质的功能来抑制病毒复制。在硬骨鱼中，目前关于 IFIT 的基因和功能的知识是有限的。在目前的工作中，我们描述了大西洋鲑鱼中的 IFIT5 直向同源物 (SsaIFIT5)，其具有特征性的四肽重复基序。我们在这里展示了编码 SsaIFIT5 的基因 ( SsaIfit5) 在各种鲑鱼组织中普遍表达，而活鱼的细菌和病毒攻击以及用重组干扰素和病原体模拟物对细胞的体外刺激触发了其转录。响应各种免疫刺激的深刻表达可归因于SsaIfit5基因推定启动子中已识别的 IFN 反应元件和各种免疫相关转录因子的结合位点。我们的结果将SsaIfit5 确定为 A.鲑鱼中的 IFN 刺激基因，并强烈表明 IFIT5 蛋白在脊椎动物的抗菌反应中具有系统发育上的保守作用。