QKI5-regulated miRNAs

microRNAs (miRNAs) accomplish a remarkable variety of biological functions. Their expression is tightly controlled, and the final production of a miRNA is dependent on the cooperation of multiple mechanisms and their net effect. Here we show that miR-124-1 is transcriptionally activated during erythroid differentiation by GATA-1, however its post-transcriptional processing is attenuated. We found that QKI5 binds to a distal QKI response element (QRE) embedded in the primary transcript of miR-124-1 (pri-124-1) and modulates Microprocessor function by direct association with DGCR8. Strikingly, Microprocessor recruitment to pri-124-1 is disrupted upon RNAi-mediated depletion of QKI5, consistent with the decrease in mature miR-124. Moreover, addition of QKI5 increases the conversion efficiency of pri-124-1 in cell-free extracts. For erythropoiesis, the decreased QKI5 leads to attenuated Microprocessor-mediated processing of pri-124-1, which confers the exquisite miRNA abundance necessary for development. This regulation also gives rise to a unique miRNA signature required for normal erythropoiesis. Thus, this QKI5-regulated miRNA processing may represent a common paradigm for erythroid development, and specifically, it may serve as a post-transcriptional fault security to prevent misexpression of certain miRNAs, that is essential for the establishment of particular gene expression patterns during development. Two samples are analyzed: K562 cells transduced with GFP lentivirus; and K562 cells transduced with QKI5-overexpressing lentivirus.