Protein molecules are the structural and functional pillars of the cell. Biologists long believed they did all the cell's heavy lifting, carrying out its functions and orchestrating the thousands of chemical reactions that help it live, grow, and respond to its environment.
But in 1982, with the help of a single-celled pond organism, Thomas R. Cech at the University of Colorado, Boulder, toppled that tenet of biology by showing that RNA, or ribonucleic acid, could act as a catalyst, sparking some of the biochemical reactions that power the cell — in addition to being a carrier of hereditary information. In those studies, Cech and his colleagues showed that RNA is more than a biological middleman, capable only of shepherding hereditary information from one molecule to another.
In announcing his finding that year, Cech, who became an HHMI investigator in 1988, demonstrated that RNA possessed catalytic powers previously attributed only to protein enzymes, which shear and splice chemical bonds in the elegant molecular interplay essential for the function of every cell. For that work, Cech and Yale University's Sidney Altman, who independently discovered the catalytic properties of RNA, were awarded the 1989 Nobel Prize in Chemistry.
Cech and his research group made their discovery with an RNA molecule from a unicellular pond microbe known as Tetrahymena. Placing unprocessed Tetrahymena RNA in a test tube, they observed that the RNA could cut and rejoin its own chemical bonds in the absence of any catalytic protein. In other words, they observed RNA's role in facilitating the complex chemical interplay of the cell for the first time.
That new knowledge not only challenged biological gospel, it was powerful evidence that there were probably other hidden avenues of catalysis within cells. Intriguingly, the finding also lent plausibility to the idea that RNA may have played a key role in the advent of life on Earth. All life requires genetic information, usually in the form of DNA. But enzymes and other proteins are required to execute the instructions encoded in DNA, leaving biologists with a classic chicken-and-egg conundrum: Which molecule came first? The discovery of catalytic RNA hints it may have been the first molecule of life, as it can perform the twin functions of carrying genetic information and acting as a catalyst.
Finally, in the context of human health, Cech's discovery suggests it might be possible to develop a new class of antiviral drugs. Catalytic RNAs, or ribozymes, are capable of cleaving viral RNA and inactivating viruses in under controlled laboratory conditions. Study of these molecules may one day lead to new antiviral agents capable of accomplishing the same feat in people to treat colds and other viral ailments. The potential would be the same for other organisms, holding out the possibility of creating therapies for important animal diseases and devising virus-resistant plants.
Photo: Paul Fetters