New research shows that if too much interfering RNA is put into a cell, then it could overtax the cell's ability to process its own microRNA. RNA is the chemical cousin of DNA, which encodes hereditary instructions in genes. RNA was once thought to be a mere messenger in the cell. But in a rush of discoveries over the last few years, scientists have found that RNA plays a more active role in controlling gene activity. They have found that cells make tiny snippets of RNA, called microRNA, that silence particular genes. And they have learned how to harness that natural mechanism to turn off any gene of their choosing by inserting the proper piece of RNA into cells.
The findings were "not a showstopper by any means" for the field of RNAi. "It's like any drug," Mark Kay (Stanford University School of Medicine) said. "The toxicity depends on the dose."