Yuexiu Zhang, Huawei Zhang, Guang-Lai Zheng, Qian Yang, Shaoxiong Yu, Jinghan Wang, Su Li, Lian-Feng Li, Hua-Ji Qiu

J Virol. 2019 Aug 14. pii: JVI.01248-19. doi: 10.1128/JVI.01248-19. [Epub ahead of print]

Abstract

In the host, many RING-domain E3 ligases have been reported to inhibit viral replication through various mechanisms. In a previous screen, we found that the porcine RING finger protein 114 (pRNF114), an RING-domain E3 ubiquitin ligase, inhibits classical swine fever virus (CSFV) replication. This study aimed to clarify the underlying antiviral mechanism of pRNF114 against CSFV. Upon CSFV infection, the pRNF114 mRNA was upregulated both in vitro and in vivo CSFV replication was significantly suppressed in PK-pRNF114 cells stably expressing pRNF114 by lentivirus-delivered system, whereas CSFV growth was enhanced in PK-15 cells with RNF114 knockout by the CRISPR/Cas9 system. The RING domain of pRNF114, which has the E3 ubiquitin ligase activity, is crucial for its antiviral activity. Mechanistically, pRNF114 interacted with the CSFV NS4B protein through their C-terminal domains, which led to the K27-linked polyubiquitination and degradation of NS4B through a proteasome-dependent pathway. Collectively, these findings indicate that pRNF114 as a critical regulator of CSFV replication and uncover a mechanism by which pRNF114 employs its E3 ubiquitin ligase activity to inhibit CSFV replication.IMPORTANCE The porcine RING finger protein 114 (pRNF114) is a member of RING-domain E3 ligases. In this study, pRNF114 is a potential anti-CSFV factor and the anti-CSFV effect of pRNF114 depends on its E3 ligase activity. Notably, pRNF114 targets and catalyzes the K27-linked polyubiquitination of the NS4B protein and then promotes proteasome-dependent degradation of NS4B, inhibiting the replication of CSFV. To our knowledge, pRNF114 is the first E3 ligase to be identified as being involved in anti-CSFV activity and targeting NS4B could be a crucial route for antiviral development.