DEAD-Box RNA Helicase 21 (DDX21) Positively Regulates the Replication of Porcine Reproductive and Respiratory Syndrome Virus via Multiple Mechanisms

Abstract

The porcine reproductive and respiratory syndrome virus (PRRSV) remains a persistent hazard in the global pig industry. DEAD (Glu-Asp-Ala-Glu) box helicase 21 (DDX21) is a member of the DDX family. In addition to its function of regulating cellular RNA metabolism, DDX21 also regulates innate immunity and is involved in the replication cycle of some viruses. However, the relationship between DDX21 and PRRSV has not yet been explored. Here, we found that a DDX21 overexpression promoted PRRSV replication, whereas knockdown of DDX21 reduced PRRSV proliferation. Mechanistically, DDX21 promoted PRRSV replication independently of its ATPase, RNA helicase, and foldase activities. Furthermore, overexpression of DDX21 stabilized the expressions of PRRSV nsp1α, nsp1β, and nucleocapsid proteins, three known antagonists of interferon β (IFN-β). Knockdown of DDX21 activated the IFN-β signaling pathway in PRRSV-infected cells, suggesting that the effect of DDX21 on PRRSV-encoded IFN-β antagonists may be a driving factor for its contribution to viral proliferation. We also found that PRRSV infection enhanced DDX21 expression and promoted its nucleus-to-cytoplasm translocation. Screening PRRSV-encoded proteins showed that nsp1β interacted with the C-terminus of DDX21 and enhanced the expression of DDX21. Taken together, these findings reveal that DDX21 plays an important role in regulating PRRSV proliferation through multiple mechanisms.

DEAD-box RNA helicase 21 interacts with porcine circovirus type 2 Cap protein and facilitates viral replication

“…The subcellular distribution of DDX21 into nucleolus is required for the RNA unwinding ( Song et al, 2017 ). DDX21 regulates viral replication through many ways, including inhibiting viral genome replication and prohibiting virus replication ( Watanabe et al, 2009 ; Abdullah et al, 2021 ; Li et al, 2022b ; Zhao et al, 2022 ). DDX21 interacts with rRNAs and snoRNAs to facilitate transcription and processing ( Flores-Rozas and Hurwitz, 1993 ).…”

“…The primers used are listed in Table 1. Cell transfection was conducted as previously described (Zhou et al, 2022b).…”

Classification, replication, and transcription of Nidovirales

“…During PRRSV infection, DDX18 redistributes from nucleus to cytoplasm and interacts with NSP2 and NSP10, to promote virus replication ( Jin et al, 2017 ). DDX21 is also translocated from nucleus to cytoplasm and then positively regulates the PRRSV replication by stabilizing the expression of PRRSV NSP1α, NSP1β, and N protein ( Li et al, 2022 ). It has been found that DDX21 interacts with NSP1β, which enhances the expression of DDX21.…”