The Yarrowia lipolytica orthologs of Sup35p assemble into thioflavin T-negative amyloid fibrils.

The translation terminator Sup35p assembles into self-replicating fibrillar aggregates that are responsible for the [PSI] prion state. The Q/N-rich N-terminal domain together with the highly charged middle-domain (NM domain) drive the assembly of Sup35p into amyloid fibrils in vitro. NM domains are highly divergent among yeasts. The ability to convert to a prion form is however conserved among Sup35 orthologs. In particular, the Yarrowia lipolytica Sup35p stands out with an exceptionally high prion conversion rate. In the present work, we show that different Yarrowia lipolytica strains contain one of two Sup35p orthologs that differ by the number of repeats within their NM domain. The Y. lipolytica Sup35 proteins are able to assemble into amyloid fibrils. Contrary to S. cerevisiae Sup35p, fibrils made of full-length or NM domains of Y. lipolytica Sup35 proteins did not bind Thioflavin-T, a well-known marker of amyloid aggregates.