(PHILADELPHIA) Tiny bits of short-lived genetic material called microRNAs, or miRNAs, have attracted enormous interest from scientists since their discovery in humans only a few years ago. Viewed most broadly, they appear to play significant roles in controlling gene expression and development in many different settings.

Now, a new study from researchers at The Wistar Institute identifies for the first time a molecular complex vital for the creation of miRNAs. This complex, dubbed the microprocessor complex, contains two proteins, one of which has been linked to DiGeorge syndrome, the most common disorder of genetic deletion in humans. A swathe of DNA containing multiple genes is missing in DiGeorge syndrome patients, and many are born with heart defects, immune deficiencies, and developmental and behavioral problems. Intriguingly, one in four also goes on to develop schizophrenia, a disorder for which causative genes have yet to be identified. The new study appears in the November 11 issue of Nature.

"Discovery of this microprocessor complex gives us important insights into the processing mechanisms that generate miRNAs in the body," says Ramin Shiekhattar, Ph.D., an associate professor at Wistar and senior author on the Nature study. "At the same time, we see that one of the components of the complex is implicated in DiGeorge syndrome, suggesting that miRNA activity or its lack may be pivotal in the disease process of that multifaceted disorder."

The genes that code for miRNAs initially gives rise to a long primary RNA molecule that must first be cut into small precursor RNA molecules before final processing into mature miRNAs. The finished miRNAs are remarkably small, only 22 nucleotides in length, but powerful. These molecules appear to work by binding to complementary regions in messenger RNA, responsible for translating genes into proteins, or even to certain stretches of DNA. Either way, the result is gene silencing, which is one of t
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Contact: Franklin Hoke
hoke@wistar.upenn.edu
215-898-3716
The Wistar Institute
17-Nov-2004

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