Newly identified prion linked to the chromatin-remodeling factor Swi1 in Saccharomyces cerevisiae

SWI/SNF, an evolutionarily conserved ATP-dependent chromatin-remodeling complex, has an important role in transcriptional regulation. In Saccharomyces cerevisiae, SWI/SNF regulates the expression of ∼6% of total genes through activation or repression. Swi1, a subunit of SWI/SNF, contains an N-terminal region rich in glutamine and asparagine, a notable feature shared by all characterized yeast prions - a group of unique proteins capable of self-perpetuating changes in conformation and function. Here we provide evidence that Swi1 can become a prion, [SWI⁺]. Swi1 aggregates in [SWI ⁺] cells but not in nonprion cells. Cells bearing [SWI⁺] show a partial loss-of-function phenotype of SWI/SNF. [SWI⁺] can be eliminated by guanidine hydrochloride treatment, HSP104 deletion or loss of Swi1. Moreover, we show [SWI⁺] is dominantly and cytoplasmically transmitted. Our findings reveal a novel mechanism of 'protein-only' inheritance that results in modification of chromatin-remodeling and, ultimately, global gene regulation.