RESUMO
The ubiquitously expressed RNA-binding proteins Roquin-1 and Roquin-2 are essential for appropriate immune cell function and postnatal survival of mice. Roquin proteins repress target mRNAs by recognizing secondary structures in their 3'-UTRs and by inducing mRNA decay. However, it is unknown if other cellular proteins contribute to target control. To identify cofactors of Roquin, we used RNA interference to screen ~1500 genes involved in RNA-binding or mRNA degradation, and identified NUFIP2 as a cofactor of Roquin-induced mRNA decay. NUFIP2 binds directly and with high affinity to Roquin, which stabilizes NUFIP2 in cells. Post-transcriptional repression of human ICOS by endogenous Roquin proteins requires two neighboring non-canonical stem-loops in the ICOS 3'-UTR. This unconventional cis-element as well as another tandem loop known to confer Roquin-mediated regulation of the Ox40 3'-UTR, are bound cooperatively by Roquin and NUFIP2. NUFIP2 therefore emerges as a cofactor that contributes to mRNA target recognition by Roquin.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Proteína Coestimuladora de Linfócitos T Induzíveis/genética , Proteínas Nucleares/genética , Proteínas de Ligação a RNA/genética , Receptores OX40/genética , Proteínas Repressoras/genética , Ubiquitina-Proteína Ligases/genética , Sequência de Aminoácidos , Animais , Sítios de Ligação , Linfócitos T CD4-Positivos/citologia , Regulação da Expressão Gênica , Células HEK293 , Células HeLa , Humanos , Proteína Coestimuladora de Linfócitos T Induzíveis/antagonistas & inibidores , Proteína Coestimuladora de Linfócitos T Induzíveis/imunologia , Sequências Repetidas Invertidas , Camundongos , Camundongos Endogâmicos C57BL , Proteínas Nucleares/antagonistas & inibidores , Proteínas Nucleares/imunologia , Conformação de Ácido Nucleico , Cultura Primária de Células , Ligação Proteica , Estabilidade de RNA , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Proteínas de Ligação a RNA/antagonistas & inibidores , Proteínas de Ligação a RNA/imunologia , Receptores OX40/antagonistas & inibidores , Receptores OX40/imunologia , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Proteínas Repressoras/imunologia , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Ubiquitina-Proteína Ligases/imunologiaRESUMO
Humoral autoimmunity paralleled by the accumulation of follicular helper T cells (T(FH) cells) is linked to mutation of the gene encoding the RNA-binding protein roquin-1. Here we found that T cells lacking roquin caused pathology in the lung and accumulated as cells of the T(H)17 subset of helper T cells in the lungs. Roquin inhibited T(H)17 cell differentiation and acted together with the endoribonuclease regnase-1 to repress target mRNA encoding the T(H)17 cell-promoting factors IL-6, ICOS, c-Rel, IRF4, IκBNS and IκBζ. This cooperation required binding of RNA by roquin and the nuclease activity of regnase-1. Upon recognition of antigen by the T cell antigen receptor (TCR), roquin and regnase-1 proteins were cleaved by the paracaspase MALT1. Thus, this pathway acts as a 'rheostat' by translating TCR signal strength via graded inactivation of post-transcriptional repressors and differential derepression of targets to enhance T(H)17 differentiation.
