The papain-like protease of avian infectious bronchitis virus has deubiquitinating activity.
Coronavirus papain-like proteases (PLPs) can act as proteases that process virus-encoded large replicase polyproteins and also as deubiquitinating (DUB) enzymes. Like the PLPs of other coronaviruses (CoVs), the avian infectious bronchitis virus (IBV) PLP catalyzes proteolysis of Gly-Gly dipeptide bonds to release mature cleavage products. However, the other functions of the IBV PLP are not well understood. In this study, we found that IBV exhibits strong global DUB activity with significant reductions of the levels of ubiquitin (Ub)-, K48-, and K63-conjugated proteins. The DUB activity exhibited a clear time dependence, with stronger DUB activity in the early stage of viral infection. Furthermore, the IBV replicase-encoded PLP, including the downstream transmembrane (TM) domain, is a DUB enzyme and dramatically reduced the level of Ub-conjugated proteins, while processing both K48- and K63-linked polyubiquitin chains. By contrast, PLP did not cause any reduction of haemagglutinin (HA)-Ub-conjugated proteins. In addition, mutations of the catalytic residues of PLP-TM, Cys1274Ser and His1437Lys, reduced DUB activity against Ub-, K48- and K63- conjugated proteins, indicating that the DUB activity of the PLP-TM wild-type protein is not completely dependent on its catalytic activity. Overall, these results demonstrate that the IBV-encoded PLP-TM functions as a DUB enzyme and suggest that IBV may interfere with the activation of host antiviral signaling pathway by degrading polyubiquitin-associated proteins.
Jiangsu Co-Innovation Center for Prevention of Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, China.
Liping
L
Yu
Jiangsu Co-Innovation Center for Prevention of Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, China.
Xiaorong
X
Zhang
Jiangsu Co-Innovation Center for Prevention of Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, China.
Tianqi
T
Wu
Jiangsu Co-Innovation Center for Prevention of Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, China.
Yuyang
Y
Wang
Jiangsu Co-Innovation Center for Prevention of Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, China.
Jie
J
Meng
Jiangsu Co-Innovation Center for Prevention of Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, China.
Qian
Q
Liu
Jiangsu Co-Innovation Center for Prevention of Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, China.
Xiaosai
X
Niu
Jiangsu Co-Innovation Center for Prevention of Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, China. ytwu@yzu.edu.cn.
Yantao
Y
Wu
D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D003001:Cloning, Molecular; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D015967:Gene Expression Regulation, Viral / Q000502:physiology*; D001351:Infectious bronchitis virus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D007668:Kidney / Q000166:cytology; D016297:Mutagenesis, Site-Directed; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
D014764:Viral Proteins; D010447:Peptide Hydrolases