title: Characterizations of two grass carp Ctenopharyngodon idella HMGB2 genes and potential roles in innate immunity.
abstract: High-mobility group box 2 (HMGB2) protein is a chromatin-associated nonhistone protein, involved in transcriptional regulation and nucleic-acid-mediated innate immune responses in mammalian. However, the function of piscine HMGB2 in innate immune responses is still unknown. In the present study, two HMGB2 homologue genes (CiHMGB2a, CiHMGB2b) were identified and characterized in grass carp (Ctenopharyngodon idella). Both CiHMGB2a and CiHMGB2b genes encode proteins with 213 amino acids, sharing 71.4% identities and containing two basic HMG boxes and an acidic tail. The deduced protein sequences showed the most identities to HMGB2a (93%) and HMGB2b (86.4%) of zebrafish (Danio rerio), respectively. Quantitative real-time RT-PCR (qRT-PCR) analysis showed that CiHMGB2a and CiHMGB2b were constitutively expressed in all the 15 tested tissues. Post grass carp reovirus (GCRV) infection, mRNA levels of CiHMGB2a and CiHMGB2b were strongly up-regulated in spleen and head kidney and mildly modulated in C. idella kidney (CIK) cells. Meanwhile, mRNA expressions of CiHMGB2a and CiHMGB2b were significantly regulated by viral pathogen associated molecular patterns (PAMPs) polyinosinic-polycytidylic potassium salt (poly(I:C)) and bacterial PAMPs lipopolysaccharide (LPS), peptidoglycan (PGN) challenge in CIK cells. In CiHMGB2a and CiHMGB2b over-expression cells, expressions of CiHMGB2a and CiHMGB2b facilitated each other; transcription levels of CiTRIF, CiMyD88, CiIPS-1 and CiMx1 were remarkably enhanced, whereas CiIFN-I was inhibited, compared with those in cells transfected with pCMV (control plasmid); after GCRV challenge, all those tested genes were up-regulated with divergent expression profiles. Antiviral activities of CiHMGB2a and CiHMGB2b were manifested by the delayed appearance of cytopathic effect (CPE) and inhibition of GCRV yield. All those results demonstrate that CiHMGB2a and CiHMGB2b not only mediate antiviral immune responses but also involve in responding to viral/bacterial PAMPs challenge, which provides novel insights into the essential role of HMGB2 in innate immunity.
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Shaanxi Key Laboratory of Molecular Biology for Agriculture, Yangling 712100, China.
authors.forename: Youliang
authors.initials: Y
authors.lastname: Rao
authors.forename: Jianguo
authors.initials: J
authors.lastname: Su
authors.forename: Chunrong
authors.initials: C
authors.lastname: Yang
authors.forename: Limin
authors.initials: L
authors.lastname: Peng
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Feng
authors.forename: Qingmei
authors.initials: Q
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002347:Carps / Q000235:genetics / Q000276:immunology* / Q000821:virology; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D005393:Fish Diseases / Q000235:genetics / Q000276:immunology / Q000821:virology; D029941:Fish Proteins / Q000145:classification / Q000235:genetics / Q000276:immunology*; D015870:Gene Expression / Q000276:immunology; D020869:Gene Expression Profiling; D024261:HMGB2 Protein / Q000145:classification / Q000235:genetics / Q000276:immunology*; D060226:Head Kidney / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D054884:Host-Pathogen Interactions / Q000276:immunology; D007113:Immunity, Innate / Q000276:immunology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D020033:Protein Isoforms / Q000145:classification / Q000235:genetics / Q000276:immunology; D012087:Reoviridae / Q000276:immunology / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013154:Spleen / Q000276:immunology / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D029941:Fish Proteins; D024261:HMGB2 Protein; D020033:Protein Isoforms
keywords: Antiviral activity; Grass carp (Ctenopharyngodon idella); Grass carp reovirus; HMGB2; Innate immunity