MYC and Miyoshi myopathy: Mechanistically, following the secretion of circHNRNPU, which encodes circHNRNPU_603aa in the bone marrows by MM cells, through the RNA-binding RGG-box region, circHNRNPU_603aa significantly regulates backsplicing of SKP2 exon and activates AMN1 to stabilize c-myc, thereby competitively inhibiting c-Myc ubiquitin (Fig. 6b) 60.