UCSF

Prions, or infectious proteins, are self-templating ordered aggregates capable of replication. One such prion, [PSI+], is caused by the aggregation of the translation termination factor Sup35 in Saccharomyces cerevisiae. Although much more amenable to experimentation, yeast prions share many characteristics with their mammalian counterparts, including the existence of prion strain variants and the ability of single amino acids to modulate prion phenotypes in a manner that's specific to a particular prion strain variant. Yeast prions propagate through a cycle that consists of prion growth, division, and partitioning to daughter cells. Chapter 2 describes investigation of how single amino acid changes affect the ability of prions to propagate, through systematically probing each step of the prion propagation cycle. This work emphasizes partitioning as a crucial step in the prion replication cycle, highlighting it as an interesting area of future study. Chapter 3 describes an attempt to create a robust in vitro system to investigate how chaperones can act as molecular motors to divide extraordinarily stable prion particles. Unfortunately, this synthetic system was ultimately unable to divide prions in vitro.