Creutzfeldt-Jakob Disease (CJD) is an unusual infectious disease of the human brain that leads to dementia and death. The most baffling fact about this and related diseases such as sheep scrapie and bovine spongiform encephalopathy (BSE, Mad Cow Disease) is that they appear to be triggered by a unique class of infectious agent known as a prion. Prions are remarkable infectious agents because they consist only of a single protein species that is a structurally altered form of a protein (called PrP) normally found in the brain. Although CJD is a comparatively rare disease in humans (approximately 1 in a million people will contract the disease in any one year), sufferers show many of the pathological features seen in individuals suffering from other more common, non-infectious diseases of the brain such as Alzheimer’s Disease and Parkinson’s Disease. Yet we know remarkably little about how prions form spontaneously to cause sporadic CJD, what triggers their formation and why they can be transmitted between individuals.
To help us address these questions we study prions that are found in Baker’s yeast (Saccharomyces cerevisiae). Yeast prions were first described almost 20 years ago and the many subsequent studies on yeast prions have revealed fascinating often surprising new insights into prion biology not least the fact that their presence can be of benefit to the host they infect rather than detrimental.