Issue Date: May 18, 2009
New Type Of Small RNA Discovered
Biologists have found a new class of small interfering RNAs, called qiRNAs, which are induced to form by DNA damage (Nature 2009, 459, 274). Small interfering RNAs are used to silence gene expression by preventing the translation of messenger RNA into protein. Physiologist Yi Liu and coworkers of the University of Texas Southwestern Medical Center uncovered qiRNAs in the filamentous fungus Neurospora crassa. The qiRNAs, so named because they interact with a protein known as QDE-2, are 20 to 21 nucleotides long, show a preference for uridine at their 5´ end, and most often originate from the region of DNA that encodes ribosomal DNA. In addition to QDE-2, the formation of qiRNAs requires the expression of QDE-1 and QDE-3, which are proteins that synthesize RNA and unwind DNA, respectively. Liu and coworkers also found that qiRNA biosynthesis requires a precursor that forms after DNA damage. They suggest that qiRNAs might play a role in DNA damage response by inhibiting protein synthesis after DNA is damaged.
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