RNAa

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Small double-stranded RNA (dsRNA) has been found to silence gene expression by an evolutionally conserved mechanism known as RNA interference or RNAi. Such dsRNAs are called small interfering RNAs or siRNA. RNAi can occur at both transcriptional and post-transcriptional levels. Surprisingly, two recent studies have found that dsRNA can also activate gene expression, a mechanism that has been termed "small RNA-induced gene activation" or RNAa.[1][2][3] It has been shown that dsRNAs targeting gene promoters induce potent transcriptional activation of associated genes. Both studies demonstrate RNAa in human cells using synthetic dsRNAs termed small activating RNAs (saRNAs). Endogenous miRNA that cause RNAa has also been found in humans.[4] It is currently unknown if RNAa is conserved in other organisms.

Another surprising observation is that gene activation by RNAa is long-lasting. Induction of gene expression has been seen to last for over ten days. The prolonged effect of RNAa could be attributed to epigenetic changes at dsRNA target sites.

[edit] References

  1. ^ Li LC, et al. Small dsRNAs induce transcriptional activation in human cells. Proc Natl Acad Sci U S A. 2006 Nov 14;103(46):17337-42. [Epub 2006 Nov 3.]
  2. ^ Janowski BA, et al. Activating gene expression in mammalian cells with promoter-targeted duplex RNAs. Nat Chem Biol. 2007 Jan 28; [Epub ahead of print]
  3. ^ Li LC (2008). "Small RNA-Mediated Gene Activation", RNA and the Regulation of Gene Expression: A Hidden Layer of Complexity. Caister Academic Press. ISBN 978-1-904455-25-7. 
  4. ^ Check E (2007). "RNA interference: hitting the on switch". Nature 448 (7156): 855–858. doi:10.1038/448855a. PMID 17713502. 

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