Regulation of gene expression by miR-144/451 during mouse erythropoiesis.

The microRNA (miRNA) locus miR-144/451 is abundantly expressed in erythrocyte precursors, facilitates their terminal maturation and protects against oxidant stress. However, the full repertoire of erythroid miR-144/451 target mRNAs and associated cellular pathways is unknown. In general, the numbers of mRNAs predicted to be targeted by a miRNA vary greatly from hundreds to thousands, and are dependent on experimental approaches. To comprehensively and accurately identify erythroid miR-144/451 target mRNAs, we compared gene knockout (KO) and wild-type fetal liver erythroblasts by RNA-sequencing, quantitative proteomics and RNA immunoprecipitation of Argonaute (Ago), a component of the RNA induced silencing complex (RISC) that binds miRNAs complexed to their target mRNAs. Argonaute bound approximately 1400 erythroblast mRNAs in a miR-144/451-dependent manner, accounting for one third of all Ago-bound mRNAs. However, only about 100 mRNAs were stabilized after miR-144/451 loss. Thus, miR-144 and miR-451 deregulate l10% of mRNAs that they bind, a characteristic that likely applies generally to other miRNAs. Using stringent selection criteria, we identified 53 novel miR-144/451 target mRNAs. One of these, Cox10 , facilitates the assembly of mitochondrial electron transport complex IV. Loss of miR-144/451 caused increased Cox10 mRNA and protein, accumulation of Complex IV, and increased mitochondrial membrane potential with no change in mitochondrial mass. Thus, miR-144/451 represses mitochondrial respiration during erythropoiesis by inhibiting the production of Cox10.