Interaction of Influenza A Nucleoprotein with Host hnRNP-C Is Implicated in Viral Replication

The Role of Long Noncoding RNA Negative Regulator of Interferon Response in the Regulation of Hantaan Virus Infection

Hantaan virus (HTNV) is prevalent in Eurasia. It causes hemorrhagic fever with renal syndrome (HFRS). Long noncoding RNAs (lncRNAs) play key roles in regulating innate immunity. Among these, lncRNA negative regulator of interferon response (NRIR) was reported as an inhibitor of several interferon (IFN)-stimulated genes. Our results showed that: NRIR expression was upregulated by HTNV infection in a type I IFN-dependent manner. The expression of NRIR in CD14+ monocytes from HFRS patients in acute phase was significantly higher than that in convalescent phase and healthy controls. HTNV infection in some HTNV-compatible cells was promoted by NRIR. NRIR negatively regulated innate immunity, especially IFITM3 expression. Localized in the nucleus, NRIR bound with HNRNPC, and knockdown of HNRNPC significantly weakened the effect of NRIR in promoting HTNV infection and restored IFITM3 expression. These results indicated that NRIR regulates the innate immune response against HTNV infection possibly through its interaction with HNRNPC and its influence on IFITM3.

hnRNPM suppressed IRF7-mediated IFN signaling in the antiviral innate immunity in triploid hybrid fish

Mammalian heterogeneous nuclear ribonucleoproteins M (hnRNPM) is a critical splicing regulatory protein that has been reported to negatively regulate the RLR signaling pathway by impairing the binding of RIG-I and MDA5 to viral RNA. To explore the role of hnRNPM in the antiviral innate immune response in teleost fish, the hnRNPM homologue of triploid fish (3nhnRNPM) has been cloned and identified in this paper. The CDS of 3nhnRNPM gene is composed of 2016 nucleotides and encodes 671 amino acids. 3nhnRNPM migrated around 71 kDa in immunoblotting assay and was mainly detected in the nucleus in nucleo-cytoplasmic separation assay and immunofluorescent staining test. When 3nhnRNPM and 3nIRF7 were co-expressed in EPC cells, 3nhnRNPM significantly reduced the 3nIRF7-induced interferon (IFN) promoter transcription. Correspondingly, the mRNA levels of the SVCV-M, -N, -P, and -G genes were noteworthily enhanced, but the transcription levels of epcIFNφ1, epcMx1, epcPKR, and epcISG15 were dramatically decreased. Additionally, the knockdown of 3nhnRNPM resulted in restricted SVCV replication and enhanced host cell antiviral activity. Furthermore, the association between 3nhnRNPM and 3nIRF7 has been identified by the co-immunoprecipitation assay. In addition, we found that 3nIRF7 was detained in the nucleus when co-expressed with 3nhnRNPM. To sum up, our data supported the conclusion that 3nhnRNPM suppressed 3nIRF7-mediated IFN signaling in the antiviral innate immunity.