title: Expression characterization, genomic structure and function analysis of fish ubiquitin-specific protease 18 (USP18) genes.
abstract: In mammals, USP18 (ubiquitin-specific protease 18) is an interferon (IFN) inducible protein and plays a role in regulation of IFN response upon viral infection. In this study, we first cloned a USP18 homologous gene from virally-infected crucian carp (Carassius auratus) blastula embryonic (CAB) cells, and later found in other fish species including zebrafish. All fish USP18 genes have 10 exons and 9 introns comparable to 11 exons and 10 introns in non-fish vertebrates. Expression analysis revealed that fish USP18 was significantly induced in vitro and in vivo by IFN and IFN stimuli. Using promoter-driven luciferase reporter assay system to explore the molecular mechanism underlying fish USP18 expression, fish USP18 was identified as a typical interferon (IFN)-stimulated gene (ISG). Intracellular poly(I:C)-triggered zebrafish USP18 expression was regulated through RLR-IFN pathway, which was consistent with the fact that fish USP18 gene promoter contained two typical IFN-stimulated response elements (ISREs). Further mutation assays revealed that the distant ISRE motif primarily contributed to the induction of zebrafish USP18 by fish IFN and IFN stimuli. Functionally, fish USP18 inhibited poly(I:C)- and IFN-triggered activation of a common ISRE-containing promoter, and attenuated transcriptional expression of some ISGs including Stat1 and PKZ by recombinant IFN. Finally, we found that fish USP18 protein was expressed in cytoplasm and exhibited an ability to interact with ISG15. These results indicate that fish USP18 likely exerts its function similar to mammalian homologs.
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China. Electronic address: ybzhang@ihb.ac.cn.
authors.forename: Yi-Bing
authors.initials: YB
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China.
authors.forename: Jian-Fang
authors.initials: JF
authors.lastname: Gui
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002347:Carps / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D003593:Cytoplasm / Q000201:enzymology; D004790:Enzyme Induction; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D007372:Interferons / Q000494:pharmacology / Q000502:physiology; D008969:Molecular Sequence Data; D011070:Poly I-C / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D064570:Ubiquitin-Specific Proteases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014452:Ubiquitins / Q000378:metabolism
chemical_list: D029941:Fish Proteins; D014452:Ubiquitins; D007372:Interferons; D064570:Ubiquitin-Specific Proteases; D011070:Poly I-C
keywords: Expression regulation; Interferon-stimulated gene; Promoter analysis; Subcellular localization; Ubiquitin-specific protease 18