title: Singapore grouper iridovirus-encoded semaphorin homologue (SGIV-sema) contributes to viral replication, cytoskeleton reorganization and inhibition of cellular immune responses.
abstract: Semaphorins are a large, phylogenetically conserved family of proteins that are involved in a wide range of biological processes including axonal steering, organogenesis, neoplastic transformation, as well as immune responses. In this study, a novel semaphorin homologue gene belonging to the Singapore grouper iridovirus (SGIV), ORF155R (termed SGIV-sema), was cloned and characterized. The coding region of SGIV-sema is 1728 bp in length, encoding a predicted protein with 575 aa. SGIV-sema contains a ~370 aa N-terminal Sema domain, a conserved plexin-semaphorin-integrin (PSI) domain, and an immunoglobulin (Ig)-like domain near the C terminus. SGIV-sema is an early gene product during viral infection and predominantly distributed in the cytoplasm with a speckled and clubbed pattern of appearance. Functionally, SGIV-sema could promote viral replication during SGIV infection in vitro, with no effect on the proliferation of host cells. Intriguingly, ectopically expressed SGIV-sema could alter the cytoskeletal structure of fish cells, characterized by a circumferential ring of microtubules near the nucleus and a disrupted microfilament organization. Furthermore, SGIV-sema was able to attenuate the cellular immune response, as demonstrated by decreased expression of inflammation/immune-related genes such as IL-8, IL-15, TNF-α and mediator of IRF3 activation (MITA), in SGIV-sema-expressing cells before and after SGIV infection. Ultimately, our study identified a novel, functional SGIV gene that could regulate cytoskeletal structure, immune responses and facilitate viral replication.
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, PR China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, 901 19th Street South, Birmingham, AL 35294, USA.
authors.forename: Huachun
authors.initials: H
authors.lastname: Cui
authors.affiliation: University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, PR China.|Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, PR China.
authors.forename: Chuanyu
authors.initials: C
authors.lastname: Guo
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, PR China.
authors.forename: Jingguang
authors.initials: J
authors.lastname: Wei
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, PR China.
authors.forename: Youhua
authors.initials: Y
authors.lastname: Huang
authors.affiliation: University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, PR China.|Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, PR China.
authors.forename: Lili
authors.initials: L
authors.lastname: Li
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, PR China.
authors.forename: Qiwei
authors.initials: Q
authors.lastname: Qin
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003001:Cloning, Molecular; D016207:Cytokines / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D003593:Cytoplasm / Q000737:chemistry; D003599:Cytoskeleton / Q000378:metabolism*; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D015536:Down-Regulation; D005399:Fishes; D015870:Gene Expression; D007111:Immunity, Cellular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D017995:Ranavirus / Q000235:genetics / Q000276:immunology* / Q000502:physiology*; D039961:Semaphorins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D014779:Virus Replication
chemical_list: D016207:Cytokines; D004279:DNA, Viral; D039961:Semaphorins