The RNA-binding protein HuR coordinately regulates GATA-3 and Th2 cytokine gene expression in dose dependent manner (P6262)

Abstract

Abstract Posttranscriptional control by RNA binding proteins (RBPs) is poorly understood. Th2 mediated diseases such as asthma, are driven by GATA-3, IL-4 and IL-13. The RBP, HuR, regulates IL-4 and IL-13 by increasing mRNA stability. We identified GATA-3, IL-4 and IL-13 as HuR targets and hypothesized HuR may be coordinately regulating Th2 differentiation by controlling mRNA stability and translatability. We made a HuR CD4+T transgenic mouse, and a HuR conditional knock out mouse (HuRfl/fl) to ablate HuR in T cells. HuR over-expression in transgenic CD4+ T cells stabilized GATA-3, IL-4 and IL-13 mRNAs, and increased mRNA, protein and Th2 polarization. HuR knock-down resulted in decreases in GATA-3, IL-4 and IL-13 expression. Findings were confirmed in human naïve and memory T cells. We defined HuR binding sites in GATA-3. Th2 cells with low HuR levels (26%) from HuRfl/+ mice, had decreases in IL-4, IL-13 and GATA-3 mRNA but not protein. Surprisingly, CD4+ T cells from HuRfl/fl mice (93% knockdown) showed increased IL-2, IL-4, IL-13 mRNA and protein. IL-4 transcription increased but mRNA stability remained unchanged. IL-2 and IL-13 transcription were unaltered but there were increases in mRNA stability. Polysomal gradient analysis revealed similar translation. We analyzed gene expression in KO vs. control CD4+ T cells to determine HuR targets. Ova challenge model of asthma corroborated ex vivo results. These data suggest HuR levels regulate Th2 cytokines and Th2 differentiation.