DDX5 RNA interactome in cultured T cells

RAR-related orphan receptor gamma (ROR t)-expressing regulatory T (ROR t+ Treg) cells play pivotal roles in preventing T cell hyperactivation and maintaining tissue homeostasis, in part, by secreting the anti-inflammation cytokine interleukin 10 (IL-10). Here, we report that Hypoxia Induced Factor 1a (HIF1alpha) is the master transcription factor for *Il10* in ROR t+ Tregs. Interestingly, this critical anti-inflammatory pathway is negatively regulated by an RNA-binding protein DEAD box helicase 5 (DDX5). As a transcriptional corepressor, DDX5 restricts the expression of HIF1 and its downstream target gene *Il10* in ROR t+ Tregs. T cell specific *Ddx5* knockout (DDX5 T) mice have augmented ROR t+ Treg suppressor activities and are better protected from intestinal inflammation. Genetic ablation or pharmacologic inhibition of HIF1a restores enteropathy susceptibility in DDX5 T mice. The DDX5-HIF1 -IL-10 pathway is conserved in mice and humans. These findings reveal potential therapeutic targets for intestinal inflammatory diseases. Primary cultured Th17 from two 8-10 weeks old wild-type (C57BL/6) female mice were subjected to UV- mediated crosslinking, lysis, and treatment with RNases, followed by immunoprecipitation (IP) of the DDX5-containing RNA complexes.