A viral deubiquitylating enzyme targets viral RNA-dependent RNA polymerase and affects viral infectivity

• Published in: The EMBO journal 2012-02, Vol.31 (3), p.741-753
• Main Authors: Chenon, Mélanie, Camborde, Laurent, Cheminant, Soizic, Jupin, Isabelle
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Biocatalysis; Biochemistry, Molecular Biology; Biodegradation; Cellular Biology; deubiquitylating enzyme; Electrophoresis, Polyacrylamide Gel; EMBO23; EMBO31; Enzymes; Life Sciences; Microbiology; Molecular Sequence Data; Pathogens; Pathology; Proteins; RNA polymerase; RNA Replicase - chemistry; RNA Replicase - metabolism; RNA, Viral - genetics; RNA-dependent RNA polymerase; Sequence Homology, Amino Acid; Substrate Specificity; Turnip yellow mosaic virus; Tymovirus - enzymology; Tymovirus - genetics; Tymovirus - pathogenicity; Ubiquitin - metabolism; ubiquitin-proteasome system; viral replication; Virology; Virulence
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/emboj.2011.424

Selective protein degradation via the ubiquitin‐proteasome system (UPS) plays an essential role in many major cellular processes, including host–pathogen interactions. We previously reported that the tightly regulated viral RNA‐dependent RNA polymerase (RdRp) of the positive‐strand RNA virus Turnip yellow mosaic virus (TYMV) is degraded by the UPS in infected cells, a process that affects viral infectivity. Here, we show that the TYMV 98K replication protein can counteract this degradation process thanks to its proteinase domain. In‐vitro assays revealed that the recombinant proteinase domain is a functional ovarian tumour (OTU)‐like deubiquitylating enzyme (DUB), as is the 98K produced during viral infection. We also demonstrate that 98K mediates in‐vivo deubiquitylation of TYMV RdRp protein—its binding partner within replication complexes—leading to its stabilization. Finally, we show that this DUB activity contributes to viral infectivity in plant cells. The identification of viral RdRp as a specific substrate of the viral DUB enzyme thus reveals the intricate interplay between ubiquitylation, deubiquitylation and the interaction between viral proteins in controlling levels of RdRp and viral infectivity. Turnip Yellow Mosaic Virus protects its replicative polymerase from degradation by the host cell ubiquitin‐proteasome system, employing deubiquitination activity of a processing protease with resemblance to OTU domain DUBs.