The [URE3] Prion in Candida

Ure2p, normally a regulator of nitrogen catabolism inSaccharomyces cerevisiae , can be a prion (infectious protein) by forming a folded in-register parallel amyloid called [URE3]. UsingS. cerevisiae as a test bed, we previously showed that Ure2p ofCandida albicans (CaUre2p) can also form a prion, but that Ure2p ofC. glabrata (CgUre2p) cannot. Here, we constructedC. glabrata strains to test whether CgUre2p can form a prion in its native environment. We find that while CaUre2p can form a [URE3] inC. glabrata , CgUre2p cannot, although the latter has a prion domain sequence more similar to that of ScUre2p than that of CaUre2p. This supports the notion that prion formation is not a conserved property of Ure2p but is a pathology arising sporadically. We find that some [URE3albicans ] variants are restricted in their transmissibility to certain recipient strains. In addition, we show that theC. glabrata HO can induce switching of theC. glabrata mating type locus.