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RNA PLAYS ROLE IN PRION SWITCH RNA appears to act as a cofactor or catalyst in change to infectious form STU BORMAN For the first time, RNA has been found to help convert cellular prion protein (PrPc), a normal brain component, to the infectious form that causes mad cow disease and other transmissible spongiform encephalopathies (TSEs). Cellular components were believed to be important in the conversion of PrPc into infectious scrapie-like prion protein (PrPSc) in the presence of a PrPSc template--but the exact factors involved were unknown. Now, specific RNAs have been shown to represent at least one of these components. The in vitro findings were made by lab technician Nathan R. Deleault, research associate Ralf W. Lucassen, and assistant professor Surachai Supattapone of the department of biochemistry at Dartmouth Medical School, Hanover, N.H. [Nature, 425, 717 (2003)]. The work doesn't negate the Nobel Prize-winning protein-only hypothesis--the notion that a PrPSc-type protein is the sole infectious agent in prion diseases. That's because the RNAs that catalyze PrPSc proliferation presumably are nucleic acids native to the host and not part of the PrPSc infectious agent per se. The discovery has potential implications for therapeutics and diagnostics. "Our findings suggest that host-encoded stimulatory RNA molecules may have a role in the pathogenesis of prion disease," the researchers note, suggesting a new target for the development of anti-TSE drugs. "They also provide a practical approach to improve the sensitivity of the diagnostic techniques based on [PrPSc] amplification." In a Nature commentary, two prion researchers note that the findings are not yet conclusive, in that RNAs identified in the in vitro experiments could still turn out to be stand-ins for other cellular components with greater in vivo access to PrPc. |
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