Second RNAi pathway emerges
Nature and Science papers find mechanism at work at transcriptional level in
human cells
By Jack Lucentini

The publication of a study in Nature this week (August 15)-combined with a
similar study in Science earlier this month (August 5)-could force a
reexamination of how RNA interference (RNAi) works, said several in the
field not involved in the studies. While RNA had been known to silence genes
post-transcriptionally, researchers found that it does so in a different
way, found previously in plants, at the transcriptional level in human
cells.

"This is a strong, strong suppressive pathway," said the lead author of the
Science paper, Kevin Morris, of the University of California, San Diego.
Morris' team found that SiRNAs targeting the promoter of a green fluorescent
protein gene transfected into human fibroblasts reduced its mRNA levels by
about 70%.

Separately, University of Tokyo researchers report in Nature that exploiting
the same basic pathway in mammary cells, they sliced two endogenous genes'
mRNA levels by more than 80%. One gene was a tumor-promoting oncogene,
erbB2; transcriptional RNAi significantly reduced cell proliferation in this
case, they wrote, suggesting therapeutic potential. Therapies might exploit
both silencing pathways simultaneously, lead author Kazunari Taira told The
Scientist: "It's very easy to mix two different siRNAs."

This second pathway could open the way for longer-lasting effects, new
therapeutic strategies, and evolutionary insights, researchers said. It
could be "an entirely new and important mechanism for regulating DNA
expression" in mammals, said Duke University's Bryan Cullen, who was not
involved in the studies. Edward Whang of Brigham and Women's Hospital,
Boston, who also was not involved in the studies, told The Scientist the
findings may recast RNAi as an unexpectedly complex system, with greater
potential for unintended consequences than suspected earlier.

Read the rest at TheScientist.com
http://www.theage.com.au/articles/2004/08/16/1092508365006.html

Posted by
Robert Karl Stonjek
---
þ RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info{at}bbsworld.com

---
 * RIMEGate(tm)V10.2áÿ* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 8/17/04 1:14:44 PM