Fig. 4

miRNA expression can be affected by neighboring clustered miRNA in trans. miR-451 is the only known miRNA whose biogenesis is Dicer-independent and also the most abundant miRNA in erythrocytes. It bypasses the global downregulation of other miRNAs that takes place in erythrocytes. This situation is caused by two elements: miR-144 and miR-451’s Dicer-independent biogenesis. After pre-miR-144 is exported to the cytoplasm, it is cleaved by Dicer and becomes miR-144. miR-144 then downregulates Dicer, resulting in a negative-feedback system. As other miRNAs have to be processed by Dicer in order to become mature miRNAs, miR-451 is the only miRNA that is not affected in this way, making it the most abundant miRNA