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Review
. 2009 Apr;174(4):1131-8.
doi: 10.2353/ajpath.2009.080794. Epub 2009 Mar 5.

MiRNAs and cancer

Rosa Visone  1 , Carlo M Croce
Affiliations
Review

MiRNAs and cancer

Rosa Visone et al. Am J Pathol. 2009 Apr.

Abstract

Cancer is the result of a complex multistep process that involves the accumulation of sequential alterations of several genes, including those encoding microRNAs (miRNAs). miRNAs are a class of 17- to 27-nucleotide single-stranded RNA molecules that regulate gene expression posttranscriptionally. A large body of evidence implicates aberrant miRNA expression patterns in most, if not all, human malignancies. This article reviews our current knowledge about miRNAs, focusing on their involvement in cancer and their potential as diagnostic, prognostic, and therapeutic tools.

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Figures

Figure 1
Figure 1
Biogenesis of miRNAs and assembly into protein complexes. miRNA precursor molecules (pri-miRNAs) fold into hairpin structures that contain imperfect base-paired stems in a two-step process catalyzed by two different RNase III-type endonucleases. Drosha first cleaves pri-miRNAs, forming ∼70 nucleotide hairpins (pre-miRNAs) in the nucleus. Subsequently, pre-miRNAs are transported to the cytoplasm by Exportin 5, where they are cleaved by Dicer to yield ∼20-bp miRNA duplexes. One miRNA strand is then selected to function as a mature miRNA, whereas the other strand is degraded. After processing, miRNAs are assembled into RNP (ribonucleic protein) complexes, called miRNPs, with proteins of the AGO family. miRNPs tether to the 3′UTR of a mRNA target to repress protein synthesis. In the case of perfect bp alignment, the miRNP complex cleaves the duplex miRNA-mRNA; however, multiple mechanisms are used on duplex miRNA:mRNA with imperfect complementary.
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