Context-Dependent IL-1 mRNA-Destabilization by TTP Prevents Dysregulation of Immune Homeostasis Under Steady State Conditions.

The bioavailability of the major pro-inflammatory cytokines IL-1α and IL-1β is tightly controlled by transcription and post-translational processing to prevent hyperinflammation. The role of mRNA decay in maintenance of physiological IL-1 amounts remained unknown. Here we show that the down-regulation of and mRNA by the mRNA-destabilizing protein TTP (gene ) is required for immune homeostasis. The TTP deficiency syndrome, a multi organ inflammation in mice, was significantly ameliorated upon deletion of the IL-1 receptor. and played non-redundant roles in triggering the pathological IL-1 signaling in mice. Accordingly, tissues from animals contained increased amounts of mRNA. Unexpectedly, TTP destabilized mRNA in cell type-specific ways as evident from RNA-Seq and mRNA stability assays. These results demonstrate that TTP-driven mRNA destabilization depends on the cellular context. Moreover, such context-defined mRNA decay is essential for keeping steady state IL-1 levels in the physiological range.