DDX5 and its associated lncRNA Rmrp modulate TH17 cell effector functions.

Abstract

Th17 lymphocytes protect mucosal barriers from infections, but also contribute to multiple chronic inflammatory diseases. Their differentiation is controlled by RORγt, a ligand-regulated nuclear receptor. We identified the DEAD-box RNA helicase DDX5 as a RORγt partner that coordinates transcription of selective Th17 genes and is required for Th17-mediated inflammatory pathologies. Surprisingly, the ability of DDX5 to interact with RORγt and co-activate its targets depends on its intrinsic RNA helicase activity and binding of a conserved nuclear long noncoding RNA (lncRNA), Rmrp, which is mutated in Cartilage-Hair Hypoplasia (CHH) patients. A targeted Rmrp mutation in mice, corresponding to one in CHH patients, abrogated the lncRNA’s chromatin recruitment, ability to potentiate DDX5-RORγt interaction and RORγt target gene transcription. Elucidation of the link between Rmrp and the DDX5-RORγt complex reveals a role for RNA helicases and lncRNAs in tissue-specific transcriptional regulation and promises new opportunities for therapeutic intervention in Th17-dependent diseases.