Fungal prion

An overview of fungal prions, particularly in Saccharomyces cerevisiae

Fungal Prions

File:S.cerevisiae PSI+.jpg

Saccharomyces cerevisiae cells exhibiting the [PSI+] prion state.

Fungal prions are infectious proteins found in fungi, particularly in yeast species such as Saccharomyces cerevisiae. Unlike conventional prions that cause disease in mammals, fungal prions are often non-pathogenic and can confer beneficial traits to their host organisms.

Prion Concept

The term "prion" was originally coined to describe proteinaceous infectious particles that cause neurodegenerative diseases in mammals, such as Creutzfeldt-Jakob disease and bovine spongiform encephalopathy. In fungi, prions are proteins that can exist in multiple conformations, one of which is self-propagating and transmissible.

Mechanism of Prion Propagation

Fungal prions propagate by inducing a conformational change in their normal cellular counterparts. This change converts the normal protein into the prion form, which can then aggregate and continue the cycle of conversion. This process is often mediated by specific regions within the protein known as prion domains.

Examples of Fungal Prions

Several prions have been identified in Saccharomyces cerevisiae, including:

• [PSI+]: This prion is formed by the Sup35 protein, a translation termination factor. The [PSI+] state results in read-through of stop codons, potentially leading to the expression of cryptic genetic information.
• [URE3]: Formed by the Ure2 protein, this prion affects nitrogen metabolism by altering the regulation of genes involved in nitrogen catabolism.
• [PIN+]: Associated with the Rnq1 protein, this prion is required for the de novo formation of other prions, such as [PSI+].

Biological Significance

Fungal prions can have significant effects on the physiology and evolution of their host organisms. They can act as epigenetic elements, providing a mechanism for heritable phenotypic variation without changes in the underlying DNA sequence. This can be advantageous in fluctuating environments, allowing rapid adaptation to new conditions.

Research and Applications

Research on fungal prions has provided insights into the mechanisms of protein folding and aggregation, which are relevant to understanding human diseases caused by protein misfolding. Additionally, fungal prions serve as model systems for studying the principles of epigenetic inheritance and protein-based inheritance.

Related pages

• Prion
• Saccharomyces cerevisiae
• Protein folding
• Epigenetics