Dicer represses the interferon response and the double-stranded RNA-activated protein kinase pathway in mouse embryonic stem cells

Abstract

Recent studies have demonstrated that embryonic stem cells (ESCs) are deficient in expressing type I interferons (IFN), the cytokines that play key roles in antiviral responses. However, the underlying molecular mechanisms and biological implications of this finding are poorly understood. In this study, we developed a synthetic RNA-based assay that can simultaneously assess multiple forms of antiviral responses. Dicer is an enzyme essential for RNA interference (RNAi), which is used as a major antiviral mechanism in invertebrates. RNAi activity is detected in wild-type ESCs but is abolished in Dicer knockout ESCs (D−/−ESCs) as expected. Surprisingly, D−/−ESCs have gained the ability to express IFN, which is otherwise deficient in wild-type ESCs. Furthermore, D−/−ESCs have constitutively active double-stranded RNA (dsRNA)-activated protein kinase (PKR), an enzyme that is also involved in antiviral response. D−/−ESCs show increased sensitivity to the cytotoxicity resulting from RNA transfection. The effects of dsRNA can be partly replicated with a synthetic B2RNA corresponding to the retrotransposon B2 short interspersed nuclear element. B2RNA has secondary structure features of dsRNA and accumulates in D−/−ESCs, suggesting that B2RNA could be a cellular RNA that activates PKR and contributes to the decreased cell proliferation and viability of D−/−ESCs. Treatment of D−/−ESCs with a PKR inhibitor and IFNβ-neutralizing antibodies increased cell proliferation rate and cell viability. Based on these findings, we propose that, in ESCs, Dicer acts as a repressor of antiviral responses and plays a key role in the maintenance of proliferation, viability, and pluripotency of ESCs.

Altered pattern of circulating miRNAs in HIV lipodystrophy perturbs key adipose differentiation and inflammation pathways

“…Other inflammatory markers, including IFN β , were generally increased but did not reach significance with knockdown of Ltbp2 . Dicer has recently been identified to repress interferons and the antiviral response in other cell types ( 51 ); thus, our data showing a trend toward increased interferon with reduced Dicer show a potential consistent effect in adipocytes.…”

DNA Damage-Induced Inflammatory Microenvironment and Adult Stem Cell Response

“…In fact, its downregulation has been shown to correlate with dsRNA accumulation and consequent IFN1 production in vitro (White et al, 2014). Interestingly, Dicer and its isoform (aviD) (Poirier et al, 2021) have been shown to be upregulated in NSCs, embryonic stem cells and adult intestinal stem cells (Kawase-Koga et al, 2010;Park et al, 2017;Gurung et al, 2021), and knock down of aviD has been shown to be related to higher levels of stem cell apoptosis upon viral infection (Poirier et al, 2021). Moreover, a DNA damage-inducible phospho-switch of Dicer has been linked with accumulation of this protein into the nucleus and consequent dsRNA clearance and prevention of RLR activation (Burger et al, 2017).…”

“…Kawase-Koga et al, 2010;Iliou et al, 2014;Park et al, 2017;Vishlaghi and Lisse, 2020;Gurung et al, 2021 …”

Untangling the roles of RNA helicases in antiviral innate immunity

“…The direct interaction of Dicer with PKR was specifically observed in cells infected with SINV and had a negative effect on PKR antiviral activity ( Fig 5C , left) [ 123 ]. Another indication of the crosstalk between Dicer and PKR was reported in mouse ESCs, where Dicer represses the IFN response as well as PKR activity upon dsRNA transfection [ 124 ]. As mentioned before, Dicer could interact with ISGs but its role in the IFN-I response is not clear yet.…”