Here and inside this issue we describe research tools developed specifically for miRNA analysis, including isolation and enrichment of the small RNA fraction, internal high specific activity labeling as well as end labeling of miRNA molecules, up and down modulation of expression, quantitative detection, and profiling via array analysis.
MicroRNAs (miRNAs) are an important class of small RNA molecules that are expressed in eukaryotes. Although the first miRNA was identified in a genetic screen in 1993 , it was not until 2001 that the breadth of the miRNA gene class was recognized with the cloning and sequencing of more than one hundred miRNAs from worms, humans, and mice [1-4]. These evolutionarily conserved, noncoding RNA molecules regulate translation of mRNAs through base pair interactions [reviewed in 5]. With some exceptions, worm and human miRNAs inhibit translation of specific mRNAs, while plant miRNAs induce mRNA degradation.
In cells, the ~22 nt mature, functional miRNAs are
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