Finally, because abrogation of the cellular RIG-I/interferon regulatory factor 3 (IRF-3) pathway can confer an advantage to HCVcc in vitro (e.g. the Huh-7.5 cells [20]), we evaluated the response of each Huh7 line to double-stranded RNA (dsRNA), an inducer of this pathway [21], [22].
Cellular proteins like RIG-I, PKR, and OAS are activated by sensing dsRNA.
We thus determined that the observed IFN-β activation requires RNA transfection, and is not the result of high cellular concentrations of RIG-I.
First, we found that this was neither due to an alteration at a very early step of RIG-I signaling, i.e. the ligand-binding capacity (Fig. 4A) nor to a RIG-I cellular mislocalization (not illustrated).
Interestingly, a potential source of natural cellular (self) dsRNA that RIG-I and/or MDA5 might need to discriminate against, has just been uncovered [ 64].
Collectively, these data suggest that REUL plays a critical role in the efficient cellular antiviral response mediated by RIG-I.
Previously, it has been demonstrated that RIG-I responds to infection by SV, VSV, NDV, and influenza virus, whereas MDA5 is involved in IFN signaling triggered by poly (I∶C) transfected into the cytoplasm [3], [19].We further determined whether REUL played a role in the cellular antiviral response mediated by RIG-I.
Even though it has been reported that RIG-I by itself does not respond to poly-I/C in mda-5−/− MEFs [12], [13], especially when poly-I/C of 4 8 kbp in length is used [26], this does not exclude the possibility that RIG-I participates in the cellular response to poly-I/C when both helicases are present, or that RIG-I can directly respond to poly-I/C when RIG-I levels are elevated.
However, the long-held paradigm of RIG-I serving as a PRR has been extended because of emerging new findings on the biological functions of RIG-I in other cellular activities (Zhang et al., 2008; Jiang et al., 2011; Boelens et al., 2014; Hou et al., 2014; Zeng et al., 2014).
The high cellular concentrations of these RNAs means RIG-I will bind at these sites despite its relatively weak affinity for RNA that is not triphosphorylated.
The briefcase was rigged to be detonated by a cellular phone, the police said.
