MicroRNAs (miRNAs) control gene expression in animals, plants, and unicellular eukaryotes by promoting degradation or repressing translation of target mRNAs. miRNA expression is often tissue specific and developmentally regulated, and regulation occurs both transcriptionally and posttranscriptionally. This regulation is crucial, as alteration of miRNA expression has been linked to human diseases, including several cancers. Here, we discuss recent studies that shed light on how multiple steps in the miRNA biogenesis pathway are regulated to modulate miRNA function in animals.

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