Using the [SWI+] prion to study protein misfolding, aggregation, and amyloid formation

Stephanie Valtierra

doi:https://doi.org/10.21985/N2GF23

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Using the [SWI+] prion to study protein misfolding, aggregation, and amyloid formation

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Saccharomyces cerevisiae contains several epigenetic elements known as yeast prions. Our laboratory discovered the yeast prion [SWI+], whose protein determinant is Swi1, a subunit of the SWI/SNF chromatin-remodeling complex. Formation of [SWI+] results in abolishment of multicellular features and a partial loss-of-function phenotype of non-glucose carbon source usage. Our laboratory previously showed that the first 38 amino acids of Swi1 propagate [SWI+]. We show here that a region as small as the first 32 amino acids of Swi1 (Swi11-32) aggregates and stably maintains and transmits [SWI+]. Regions smaller than Swi11-32 are either incapable of aggregation or unstably propagate [SWI+]. When fused to Sup35MC, the [PSI+] determinant lacking its prion domain (PrD), Swi11-31 and Swi11-32 can act as transferable PrDs. Thus, an NH2-terminal region of ~30 amino acids of Swi1 contains all necessary information for in vivo prion formation, maintenance, and transmission. This PrD is unique in size and composition: it is glutamine-free, asparagine-rich, and the smallest defined to date. Our results broaden our understanding of what features allow a protein region to serve as a PrD. In addition to our previous studies, our laboratory recently designed a novel reporter system that can faithfully report the prion status of Swi1. High-throughput screens were conducted to identify compounds that can inhibit or eliminate [SWI+] and obtained several promising hits. Using secondary assays, we confirmed prion loss after treatment with anti-[SWI+] compounds. Furthermore, we examined the ability of the selected compounds to eliminate other yeast prions – including [PSI+], [URE3], and [MOT3+] – and observed diverse curing abilities. Our results suggest that our novel reporter system is a useful method for finding potential anti-prion molecules and future work will aim to determine the mechanism of action of the compounds. Our studies will allow us to develop chemical probes for the study of prion biology and potentially result in the development of therapeutics for neurodegenerative diseases that are tightly associated to prion-like behaviors of various aggregation-prone proteins.

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