Mechanism of yeast prion protein aggregation and strain formation

Abstract

OF THE DISSERTATION Mechanism of yeast prion protein aggregation and strain formation By Tejas Baba Chandrashekar Kalastavadi Doctor of Philosophy in Biology and Biomedical Sciences (Molecular Genetics and Genomics) Washington University in Saint Louis, 2010 Professor Heather L. True, Chairperson Misfolding and aggregation of the prion protein (PrP) causes fatal neurodegenerative diseases in many mammalian species, including humans. Mutations in the gene encoding PrP are associated with ~15% of the incidences, while, the vast majority of the cases are sporadic. Interestingly, prion diseases also display pathological variation, suggesting that there are multiple different strains. To elucidate the mechanism of prion protein aggregation and strain formation, I have taken advantage of the yeast prions [PSI+] and [RNQ+] and their protein determinants Sup35p and Rnq1p, respectively. Using a Sup35-PrP chimera, I have investigated the effect of the disease associated oligopeptide repeat domain (ORD) expansions of PrP, on prion propagation and amyloid fiber formation. We previously determined that these chimeric proteins maintain the [PSI+] yeast prion phenotype. Interestingly, we noted that the repeat expanded chimeric prions maintained a stronger strain of [PSI+]. Investigations of the chimeric proteins in vitro revealed that repeatexpansions also increase aggregation propensity. However, despite the increased