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Large and Giant DNA Viruses

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Front. Microbiol. | doi: 10.3389/fmicb.2018.02798

Ubiquitin–Proteasome System is Required for Efficient Replication of Singapore Grouper Iridovirus

Xiaohong Huang1, Shina Wei1, Songwei Ni1,  Qiwei Qin1 and  Youhua Huang1*
  • 1South China Agricultural University, China

The ubiquitin–proteasome system (UPS) serves as the major intracellular pathway for protein degradation and plays crucial roles in several cellular processes. However, little is known about the potential actions of the UPS during fish virus infection. In this study, we elucidated the possible roles of UPS in the life cycle of Singapore grouper iridovirus (SGIV); a large DNA virus that usually causes serious systemic diseases with high mortality in groupers. Data from transcriptomic analysis of differentially expressed genes illustrated that expression of 65 genes within the UPS pathway, including ubiquitin encoding, ubiquitination, deubiquitination and proteasome, was up- or down-regulated during SGIV infection. Using different proteasome inhibitors, inhibition of the proteasome decreased SGIV replication in vitro, accompanied by inhibition of virus assembly site formation, and viral gene transcription and protein transportation. Over-expression of ubiquitin partly rescued the inhibitory effect of ubiquitin inhibitor on SGIV replication, suggesting that UPS was required for fish iridovirus infection in vitro. Viral or host proteins regulated by proteasome inhibition during SGIV infection were investigated with two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Sixty-two differentially expressed proteins, including 15 viral and 47 host proteins, were identified after SGIV infection. The host proteins were involved in ubiquitin-mediated protein degradation, metabolism, cytoskeleton, macromolecular biosynthesis, and signal transduction. Among them, 11 proteins were negatively regulated upon MG132 treatment during SGIV infection. This is believed to be the first study to provide evidence that UPS was essential for fish virus infection and replication.

Keywords: Proteasome, Ubiquitin, Iridovirus, Grouper, viral replication

Received: 05 Aug 2018; Accepted: 31 Oct 2018.

Edited by:

Jonatas Abrahao, Universidade Federal de Minas Gerais, Brazil

Reviewed by:

Eric R. Aguiar, Federal University of Bahia, Brazil
Ludmila Karen D. Silva, Délégation Alsace (CNRS), France
Alice Abreu Torres, University of Cambridge, United Kingdom  

Copyright: © 2018 Huang, Wei, Ni, Qin and Huang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Youhua Huang, South China Agricultural University, Guangzhou, China, huangyh@scau.edu.cn