A mutation within the C‐terminal domain of Sup35p that affects [PSI+] prion propagation

• Published in: Molecular microbiology Vol. 81; no. 3; pp. 640 - 658
• Main Authors: Kabani, Mehdi, Cosnier, Bruno, Bousset, Luc, Rousset, Jean‐Pierre, Melki, Ronald, Fabret, Céline
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.08.2011; Blackwell; Wiley
• Subjects: Amino Acid Substitution; Biochemistry, Molecular Biology; Biological and medical sciences; Cells; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Epigenetics; Fundamental and applied biological sciences. Psychology; Life Sciences; Medical sciences; Microbial Viability; Microbiology; Microbiology and Parasitology; Mutant Proteins - genetics; Mutant Proteins - metabolism; Mutation; Mutation, Missense; Neurology; Non conventional transmissible agents; Peptide Termination Factors - genetics; Peptide Termination Factors - metabolism; Prions - genetics; Prions - metabolism; Protein Denaturation; Protein Multimerization; Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Yeast; Yeasts; Prion; Mutation
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2011.07719.x

Summary The epigenetic factor [PSI+] in the yeast Saccharomyces cerevisiae is due to the prion form of Sup35p. The N‐terminal domain of Sup35p (N), alone or together with the middle‐domain (NM), assembles in vitro into fibrils that induce [PSI+] when introduced into yeast cells. The Sup35p C‐terminal domain (C), involved in translation termination, is essential for growth. The involvement of Sup35p C‐terminal domain into [PSI+] propagation is subject to debate. We previously showed that mutation of threonine 341 within Sup35p C‐domain affects translation termination efficiency. Here, we demonstrate that mutating threonine 341 to aspartate or alanine results in synthetic lethality with [PSI+] and weakening of [PSI+] respectively. The corresponding Sup35D and Sup35A proteins assemble into wild‐type like fibrils in vitro, but with a slower elongation rate. Moreover, cross‐seeding between Sup35p and Sup35A is inefficient both in vivo and in vitro, suggesting that the point mutation alters the structural properties of Sup35p within the fibrils. Thus, Sup35p C‐terminal domain modulates [PSI+] prion propagation, possibly through a functional interaction with the N and/or M domains of the protein. Our results clearly demonstrate that Sup35p C‐terminal domain plays a critical role in prion propagation and provide new insights into the mechanism of prion conversion.