A prion accelerates proliferation at the expense of lifespan.

Cells make different proteins to perform different tasks. Each protein is a long chain of building blocks called amino acids that must fold into a particular shape before it can be useful. Some proteins can fold in more than one way, a normal form and a ‘prion’ form. Prions are unusual in that they can force normally folded proteins with the same amino acid sequence as them to refold into new prions. This means that a single prion can make many more that are inherited when cells divide. Some prions can cause disease, but others may be beneficial. Pus4 is a yeast protein that is typically involved in modifying ribonucleic acids, molecules that help translate genetic information into new proteins. Sometimes Pus4 can adopt a beneficial prion conformation called [BIG+]. When yeast cells have access to plenty of nutrients, [BIG+] helps them grow faster and larger, but this comes at the cost of a shorter lifespan. Garcia, Campbell et al. combined computational modeling and experiments in baker’s yeast (Saccharomyces cerevisiae) to investigate the role of [BIG+]. They found that the prion accelerated protein production, leading to both faster growth and a shorter lifespan in these cells, even without any changes in gene sequence. Garcia, Campbell et al.’s findings explain the beneficial activity of prion proteins in baker’s yeast cells. The results also describe how cells balance a tradeoff between growth and lifespan without any changes in the genome. This helps to highlight that genetics do not always explain the behaviors of cells, and further methods are needed to better understand cell biology.