Oncogenic biogenesis of pri-miR-17~92

The microRNAs encoded by the miR-17~92 polycistron are commonly overexpressed in cancer and orchestrate a wide range of oncogenic functions. Here, we identify a novel mechanism for miR-17~92 oncogenic function through the disruption of endogenous miRNA processing. We show that upon oncogenic overexpression of the miR-17~92 primary transcript (pri-miR-17~92), the Microprocessor complex remains associated with partially processed intermediates that aberrantly accumulate. These intermediates reflect a series of hierarchical and conserved steps in the early processing of the pri-miR-17~92 transcript. Encumbrance of the Microprocessor by miR-17~92 intermediates leads to the broad, but selective, downregulation of co-expressed polycistronic miRNAs, including miRNAs derived from tumour suppressive miR-34b/c, and from the Dlk1-Dio3 polycistrons. We propose that the newly identified steps of polycistronic miR-17~92 biogenesis contribute to the oncogenic re-wiring of gene regulation networks. Our results reveal new functional paradigms for polycistronic miRNAs in cancer. SRA Study: SRP117775 / SRA Bioproject: PRJNA407603 / miRNA-seq on isogenic B-cells with 3 levels of miR-17~92 (flox, deleted, overexpressed), and similarly on MEF (in triplicates). Also on MEF deleted miR-17~92 with overexpressed miR-290~295 or empty plasmid control (in triplicates)