ReviewNoncoding RNAs

Outside the coding genome, mammalian microRNAs confer structural and functional complexity

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Sci. Signal.  17 Mar 2015:
Vol. 8, Issue 368, pp. re2
DOI: 10.1126/scisignal.2005813

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Protein-coding genes are regulated posttranscriptionally by microRNAs (miRNAs). These small noncoding RNAs add substantial complexity to the molecular networks that underlie development, physiology, and disease. Many miRNAs exhibit unique gene structures, frequent functional redundancy, and complex biogenesis regulation, which contribute to their diversity and versatility. In this review, which contains 5 figures, 2 tables, and 159 references, we discuss how these unique features of miRNAs provide insights into the functional complexity of mammalian genomes.


MicroRNAs (miRNAs) comprise a class of small, regulatory noncoding RNAs (ncRNAs) with pivotal roles in posttranscriptional gene regulation. Since their initial discovery in 1993, numerous miRNAs have been identified in mammalian genomes, many of which play important roles in diverse cellular processes in development and disease. These small ncRNAs regulate the expression of many protein-coding genes posttranscriptionally, thus adding a substantial complexity to the molecular networks underlying physiological development and disease. In part, this complexity arises from the distinct gene structures, the extensive genomic redundancy, and the complex regulation of the expression and biogenesis of miRNAs. These characteristics contribute to the functional robustness and versatility of miRNAs and provide important clues to the functional significance of these small ncRNAs. The unique structure and function of miRNAs will continue to inspire many to explore the vast noncoding genome and to elucidate the molecular basis for the functional complexity of mammalian genomes.

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