Demarest, K. | Search bioRxiv

bioRxiv2018

Concerted 2-5A-Mediated mRNA Decay and Transcription Reprogram Protein Synthesis in dsRNA Response

RNA degradation by RNase L during 2-5A-mediated decay (2-5AMD) is a conserved mammalian stress response to viral and endogenous double-stranded RNA (dsRNA). 2-5AMD onsets rapidly and facilitates a switch of protein synthesis from homeostasis to production of interferons (IFNs). To understand the mechanism of this protein synthesis reprogramming, we examined 2-5AMD in human cells. 2-5AMD triggers polysome collapse characteristic of a translation initiation defect, but translation initiation complexes and ribosomes purified from the translation-arrested cells remain functional. Using spike-in RNA-seq we found that basal messenger RNAs (mRNAs) rapidly decay, while mRNAs encoding IFNs and IFN-stimulated genes evade 2-5AMD and accumulate. The IFN evasion results from the combined effect of better mRNA stability and positive feedback amplification in the IFN response. Therefore, 2-5AMD and transcription act in concert to revamp the cellular mRNA composition. The resulting preferential accumulation of innate immune mRNAs establishes \"prioritized\" synthesis of defense proteins.

cell biology↗

bioRxiv2018

Realtime 2-5A kinetics suggests interferons β and {lambda} evade global arrest of translation by RNase L

Cells of all mammals recognize double-stranded RNA (dsRNA) as a foreign material. In response, they release interferons (IFNs) and activate a ubiquitously expressed pseudokinase/endoribonuclease RNase L. RNase L executes regulated RNA decay and halts global translation. Here we developed a biosensor for 2,5-oligoadenylate (2-5A), the natural activator of RNase L. We found that 2-5A was acutely synthesized by cells in response to dsRNA sensing, which immediately triggered cellular RNA cleavage by RNase L and arrested host protein synthesis. However, translation-arrested cells still transcribed IFN-stimulated genes (ISGs) and secreted IFNs of types I and III (IFN-{beta} and IFN-{lambda}). Our data suggests that IFNs escape from the action of RNase L on translation. We propose that 2-5A/RNase L pathway serves to rapidly and accurately suppress basal protein synthesis, preserving privileged production of defense proteins of the innate immune system.\n\nSignificanceRNase L is a mammalian enzyme that can stop global protein synthesis during interferon response. Cells must balance the need to make interferons (which are proteins) with the risk to lose cell-wide translation due to RNase L. This balance can most simply be achieved if RNase L was activated late in the interferon response. However, we show by engineering a biosensor for the RNase L pathway, that on the contrary, RNase L activation precedes interferon synthesis. Further, translation of interferons evades the action of RNase L. Our data suggest that RNase L facilitates a switch of protein synthesis from homeostasis to specific needs of innate immune signaling.

cell biology↗