Using E. coli as an experimental system to study the behavior of prion-like proteins

Prions are infectious, self-propagating protein aggregates that have been uncovered in evolutionary divergent members of the eukaryotic domain of life. It is not known whether prokaryotic organisms contain proteins that exhibit prion-like behavior. However, studies have shown that the E. coli cytoplasm can support conversion of the well-characterized Saccharomyces cerevisiae yeast prion protein Sup35 into the prion form and that this conversion, like in the yeast system, is dependent on the presence of amyloid aggregates of another yeast prion protein, a so-called PIN factor. It is interesting that the bacterial system recapitulates the in vivo requirements for Sup35 prion formation in the native yeast system despite the fact that bacteria diverged from eukaryotes ~2.2 billion years ago. In yeast, once formed, the Sup35 prion is stably propagated and this process is independent of the PIN factor. Using the same yeast prion protein, Sup35, in CHAPTER 2 we show that prion aggregates can be maintained for up to 90 generations in the bacterial cytoplasm and that these aggregates are still infectious when transformed into yeast.