pipeline.corante.com
...Here's a perfect example, since I was just expressing some doubts about the immediate commercial potentials of RNA interference the other day. In a paper coming out in PNAS, a group at UCSF was investigating the use of some small double-stranded RNAs, just the sort of thing that can be used for RNAi experiments. But they found (to their great surprise) that their experiments were stimulating the transcription of their targeted genes, rather than shutting them down. Needless to say, this was not what anyone expected, and I'll bet the folks involved repeated these things many, many times before they could trust their own eyes. There are plenty of other people who won't believe it until they've seen it with theirs.
On a molecular biology level, it's hard to say just what's going on. The authors, according to this news item from Science (probably subscriber-only) say that they've found some rules about which genes will be susceptible to the technique and which won't, which will be released soon. (Translation: as soon as they can be reasonably sure that they won't make fools of themselves - this paper took enough nerve as it is).
The Science article includes a good deal of if-this-holds-up language, which is appropriate for such a weird discovery. (Are the editors there wondering why they didn't get a chance to publish the article themselves, or did they have the chance and turn it down?) At any rate, if-it-holds-up this effect will simultaneously complicate the RNAi field a great deal (it was gnarly enough already, thanks) and also open a door to some really unusual experiments. Upregulating genes isn't very easy, and there are no doubt many ideas that have been waiting on a way to do it. There are therapeutic possibilities, too, naturally - but they'll have to wait on the same difficulties as the other RNA therapies.
Anyway, I'm happy to see this. It opens up some completely new biology, and it opens a door to a potential Nobel for the discoverers should everything work out. And it always cheers me up when something totally unexpected flies down like this and lands on the lawn...
The abstract -
Small dsRNAs induce transcriptional activation in human cells
Long-Cheng Li *, Steven T. Okino, Hong Zhao, Deepa Pookot, Robert F. Place, Shinji Urakami, Hideki Enokida, and Rajvir Dahiya *
Department of Urology, Veterans Affairs Medical Center and University of California, San Francisco, CA 94121
Edited by Mark T. Groudine, Fred Hutchinson Cancer Research Center, Seattle, WA, and approved September 28, 2006 (received for review August 15, 2006)
Recent studies have shown that small noncoding RNAs, such as microRNAs and siRNAs, regulate gene expression at multiple levels including chromatin architecture, transcription, RNA editing, RNA stability, and translation. Each form of RNA-dependent regulation has been generally found to silence homologous sequences and collectively called RNAi. To further study the regulatory role of small RNAs at the transcriptional level, we designed and synthesized 21-nt dsRNAs targeting selected promoter regions of human genes E-cadherin, p21WAF1/CIP1 (p21), and VEGF. Surprisingly, transfection of these dsRNAs into human cell lines caused long-lasting and sequence-specific induction of targeted genes. dsRNA mutation studies reveal that the 5' end of the antisense strand, or "seed" sequence, is critical for activity. Mechanistically, the dsRNA-induced gene activation requires the Argonaute 2 (Ago2) protein and is associated with a loss of lysine-9 methylation on histone 3 at dsRNA-target sites. In conclusion, we have identified several dsRNAs that activate gene expression by targeting noncoding regulatory regions in gene promoters. These findings reveal a more diverse role for small RNA molecules in the regulation of gene expression than previously recognized and identify a potential therapeutic use for dsRNA in targeted gene activation. |
