Molecular Biology

Mighty Miniscule RNAs

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Science  06 Jul 2012:
Vol. 337, Issue 6090, pp. 15
DOI: 10.1126/science.337.6090.15-c

An ever-increasing number of small RNAs—ranging in size from ∼20 to 400 nucleotides (nt) in length—are being found that regulate gene expression in both prokaryotes and eukaryotes. A class of tiny RNAs, known as nanoRNAs because of their minuscule size (∼2 to 4 nt), have previously been shown to prime transcription initiation in vitro by being directly incorporated into a target transcript.

By overexpressing the “nanoRNases” oligoribonuclease (Orn) and NrnB, Vvedenskaya et al. were able to reduce the levels of nanoRNAs in Escherichia coli to demonstrate that for specific genes, the tiny RNAs can influence transcription start-site selection during stationary phase growth. The nanoRNAs were also able to regulate some of these genes (tomB and bhsA), stimulating their levels during stationary-phase growth. Genome-wide analysis indicated that the promoters of many of the genes sensitive to growth phase–dependent nanoRNA-mediated start-site control have a specific sequence element that determines, in part, whether the promoter will be targeted by nanoRNA-mediated priming. NanoRNAs might stimulate de novo transcription initiation, or they could increase RNA stability through the addition of a U and/or a hydroxyl (both characteristic of nano RNAs) to the 5′ end of the RNA.

Gene. Dev. 26, 10.1101/gad.192732.112 (2012).

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