A New Role for Prions

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NIGMS Communications Office

For good reason, a poorly understood group of proteins called prions has gained a notorious reputation in recent years. These proteins have been implicated in a variety of serious brain-destroying diseases, perhaps the most famous of which is Creutzfeldt-Jakob disease, the human version of so-called "mad cow" disease. Despite a substantial amount of research into how prions cause disease, scientists remain puzzled as to what normal functions, if any, prions may participate in within a cell. To learn more about prion function, researchers have been studying prions in yeast cells. Yeast prions are different from the prions that cause mammalian diseases and do not pose any health threat. But yeast prions replicate in the same very unusual way mammalian prions do: They have the uncanny ability to change their shape and cause a chain reaction that makes other proteins of the same type change their shape, too. In the case of prions in mammals, this is associated with a deadly disease, but the yeast prion simply changes the fidelity of protein synthesis.

Dr. Susan Lindquist of the University of Chicago has discovered a new and unexpected "normal" role for prions: They may help to shape the course of evolution. Lindquist and postdoctoral fellow Dr. Heather True grew prion-containing yeast cells in 150 different conditions--varying temperature, nutrient source, and other factors, such as the presence of antibiotics or other chemicals. Remarkably, in each of seven different yeast strains the researchers tested, the prion produced a completely different set of growth properties. This meant that the cells had been stockpiling genetic changes that went completely unnoticed until the prion turned them on. Lindquist reasons that in the presence of prions, the increased diversity of a cell's protein repertoire may offer the cell a means to deal with ever-changing environmental conditions, all without affecting DNA and altering the genetic code.

Yeast cells are cheaper and easier to work with than are mammals. As such, studies in yeast promise to provide new insights into how prion proteins change their shape and function. Lindquist's new findings may help researchers devise ways to treat and perhaps prevent prion-related neurodegenerative diseases in mammals. The work may also help scientists reconcile debates about how evolution takes place--in spurts or in a more gradual manner.


True H, Lindquist SL. A yeast prion provides a mechanism for genetic variation and phenotypic diversity. Nature 2000;407:477-83.

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Writer: Alison Davis, Science Writing Contractor