Regulation of miR-155 biogenesis in cystic fibrosis lung epithelial cells: Antagonistic role of two mRNA-destabilizing proteins, KSRP and TTP

Cystic fibrosis (CF) is characterized by a massive pro-inflammatory phenotype in the lung arising from profound expression of inflammatory genes, including interleukin-8 (IL-8). We have previously reported that IL-8 mRNA is stabilized in CF lung epithelial cells, resulting in concomitant hyper-expression of IL-8 protein through elevated expression of miR-155. We therefore investigated what factors promote the enhanced aberrant expression of miR-155 in CF. Here we report for the first time, the role of mRNA-destabilizing inflammatory RNA-binding proteins, KSRP and TTP, in the regulation of miR-155 biogenesis in CF lung epithelial cells. We find that KSRP and TTP have an antagonistic role in miR-155 biogenesis. While KSRP promotes enhanced processing of miR-155 precursors to mature miR-155, over-expression of TTP in the CF lung epithelial cells suppresses expression of miR-155. We find that TTP induces the expression of miR-1, which appears to be a regulator of miR-155 biogenesis in CF lung epithelial cells. These data provide novel insights into the mechanisms that induce hyper-inflammatory phenotype of CF, and are potential candidates for anti-inflammatory therapeutics for CF.