Increased [PSI+] appearance by fusion of Rnq1 with the prion domain of Sup35 in Saccharomyces cerevisiae.
During propagation, yeast prions show a strict sequence preference that confers the specificity of prion assembly. Although propagations of [PSI(+)] and [RNQ(+)] are independent of each other, the appearance of [PSI(+)] is facilitated by the presence of [RNQ(+)]. To explain the [RNQ(+)] effect on the appearance of [PSI(+)], the cross-seeding model was suggested, in which Rnq1 aggregates act as imperfect templates for Sup35 aggregation. If cross-seeding events take place in the cytoplasm of yeast cells, the collision frequency between Rnq1 aggregates and Sup35 will affect the appearance of [PSI(+)]. In this study, to address whether cross-seeding occurs in vivo, a new [PSI(+)] induction method was developed that exploits a protein fusion between the prion domain of Sup35 (NM) and Rnq1. This fusion protein successfully joins preexisting Rnq1 aggregates, which should result in the localization of NM around the Rnq1 aggregates and hence in an increased collision frequency between NM and Rnq1 aggregates. The appearance of [PSI(+)] could be induced very efficiently, even with a low expression level of the fusion protein. This study supports the occurrence of in vivo cross-seeding between Sup35 and Rnq1 and provides a new tool that can be used to dissect the mechanism of the de novo appearance of prions.
Choe
Young-Jun
YJ
Department of Biological Sciences, Laboratory of Macromolecular Interactions, and Institute of Microbiology, Seoul National University, Seoul 151-742, Korea.
Ryu
Yangkyun
Y
Kim
Hyun-Jin
HJ
Seok
Yeong-Jae
YJ
D004252:DNA Mutational Analysis; D005656:Fungal Proteins; D015966:Gene Expression Regulation, Fungal; D007700:Kinetics; D046911:Macromolecular Substances / Q000737:chemistry / Q000378:metabolism; D010454:Peptide Termination Factors / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011328:Prions / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
D005656:Fungal Proteins; D046911:Macromolecular Substances; D010454:Peptide Termination Factors; D011328:Prions; C404807:RNQ1 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; C068068:SUP35 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins