Rainbow trout DUBA inhibits type I interferon signaling by deubiquitinating TRAF3

Deubiquitinating enzyme A (DUBA), a member of the ovarian tumor (OTU) subfamily of deubiquitinases (DUBs), is recognized for its negative regulatory role in type I interferon (IFN) expression downstream of Toll-like receptor 3 (TLR3). However, its involvement in the TLR3 signaling pathway in fish remains largely unexplored. In this study, we investigated the regulatory role of DUBA (OmDUBA) in the TLR3 response in rainbow trout (Oncorhynchus mykiss). OmDUBA features a conserved OTU domain, and its expression increased in RTH-149 cells following stimulation with the TLR3 agonist poly(I:C). Gain- and loss-of-function experiments demonstrated that OmDUBA attenuated the activation of TANK-binding kinase 1 (TBK1), resulting in a subsequent reduction in type I IFN expression and IFN-stimulated response element (ISRE) activation in poly(I:C)-stimulated cells. OmDUBA interacted with TRAF3, a crucial mediator in TLR3-mediated type I IFN production. Under poly(I:C) stimulation, there was an augmentation in the K63-linked polyubiquitination of TRAF3, a process significantly inhibited upon OmDUBA overexpression. These findings suggest that OmDUBA may function similarly to its mammalian counterparts in downregulating the poly(I:C)-induced type I IFN response in rainbow trout by removing the K63-linked ubiquitin chain on TRAF3. Our study provides novel insights into the role of fish DUBA in antiviral immunity.