Robust expression of vault RNAs induced by influenza A virus plays a critical role in suppression of PKR-mediated innate immunity

Abstract

Protein kinase R (PKR) is a vital component of host innate immunity against viral infection. However, the mechanism underlying inactivation of PKR by influenza A virus (IAV) remains elusive. Here, we found that vault RNAs (vtRNAs) were greatly induced in A549 cells and mouse lungs after infection with IAV. The viral NS1 protein was shown to be the inducer triggering the upregulation of vtRNAs. Importantly, silencing vtRNA in A549 cells significantly inhibited IAV replication, whereas overexpression of vtRNAs markedly promoted the viral replication. Furthermore, in vivo studies showed that disrupting vtRNA expression in mice significantly decreased IAV replication in infected lungs. The vtRNA knockdown animals exhibited significantly enhanced resistance to IAV infection, as evidenced by attenuated acute lung injury and spleen atrophy and consequently increased survival rates. Interestingly, vtRNAs promoted viral replication through repressing the activation of PKR and the subsequent antiviral interferon response. In addition, increased expression of vtRNAs was required for efficient suppression of PKR by NS1 during IAV infection. Moreover, vtRNAs were also significantly upregulated by infections of several other viruses and involved in the inactivation of PKR signaling by these viruses. These results reveal a novel mechanism by which some viruses circumvent PKR-mediated innate immunity.

Maf1 phenotypes and cell physiology

“…Indeed, the functional diversity of Pol III transcripts continues to grow with better understanding of their canonical activities (e.g. for Y RNAs and Vault RNAs, [3,4]) and with new research showing that many Pol III transcripts can be cleaved into smaller functional RNA molecules [5]. …”

The human vault RNA enhances tumorigenesis and chemoresistance through the lysosome

“…Accumulating evidence revealing a key role of the small non-coding vtRNA1-1 in conferring cellular resistance against cell death via chemoresistance 7,12 and viral defence and apoptosis 4,8,13,48 , lead us to further investigate the involvement of vtRNA1-1 in tumorigenesis and cancer progression. In agreement with its previously described function, we observed a modulation of vtRNA1-1 expression in response to apoptosis induced by physical and mechanical stress in primary human hepatocytes and liver-derived clinical biopsies (Fig.…”

Identification of lncRNA‐155 encoded by MIR155HG as a novel regulator of innate immunity against influenza A virus infection

“…Briefly, for overexpression cell lines, human MIR155HG coding sequence (NCBI Accession: NR_001458.3) was cloned from A549 by RT-PCR and the 400 b segment at 5′ end was synthesized by Table S1). cDNA fragments for overexpression or shRNAs DNA sequences were cloned into the pNL or pSIH lentivirus vectors, respectively, as previously described Li et al, 2015). RIG-I KO cell line was generated using CRISPR-Cas9 system as previously described (Ran et al, 2013).…”

“…Knockdown cell lines were generated by stably expressing specific short hairpin RNAs (shRNAs) targeting the particular genes (list of shRNAs used are listed in Table S1). cDNA fragments for overexpression or shRNAs DNA sequences were cloned into the pNL or pSIH lentivirus vectors, respectively, as previously described Li et al, 2015). RIG-I KO cell line was generated using CRISPR-Cas9 system as previously described (Ran et al, 2013).…”

“…Recently, a great attention has been paid to noncoding RNAs (ncRNAs) as they have been extensively reported to play various key roles in the regulation of cellular response and metabolic pathways (Cech & Steitz, 2014;Yang et al, 2019). ncRNAs include various categories of RNAs, among them, long noncoding RNAs (lncRNAs) are the most substantial ncRNAs regulating the immune response to viral infection Li et al, 2015;Maarouf, Rai, Goraya, & Chen, 2018;Ouyang et al, 2014;Ouyang, Hu, & Chen, 2016). IAV is reported to induce or suppress expression of numerous lncRNAs (Ma, Ouyang, Wei, Maarouf, & Chen, 2016;Ouyang et al, 2016).…”