[Chimeric yeast prions with unstable inheritance]

Area of Science:

• Molecular Biology
• Yeast Genetics
• Prion Biology

Background:

• The Saccharomyces cerevisiae [PSI] factor is a prion form of the translation termination factor eRF3 (Sup35p).
• Induction and maintenance of the [PSI] factor are dependent on a specific prionizing peptide within Sup35p.
• The [PIN] factor, another prion, also influences [PSI] factor dynamics.

Purpose of the Study:

• To investigate the role of the prionizing peptide in inducing the [PSI] factor.
• To determine if a hybrid protein containing the Sup35p prionizing domain can induce a [PSI]-like state.
• To assess the requirements for [PSI] factor induction, including the prionizing peptide and the [PIN] factor.

Main Methods:

• Fusion of the N-terminal prionizing domain of Sup35p with the purine biosynthesis enzyme Ade2p to create NM-Sup35p::Ade2p.
• Transformation of yeast cells with a centromeric plasmid encoding the NM-Sup35p::Ade2p hybrid protein.
• Assessment of nonsense suppression as an indicator of [PSI] factor induction.

Main Results:

• Transformation with NM-Sup35p::Ade2p induced a [PSI]-like factor in yeast cells, evidenced by efficient nonsense suppression.
• The induction of the [PSI]-like factor was dependent on the presence of the prionizing peptide in the hybrid protein.
• The suppressory effect also required the prionizing peptide in the chromosomal Sup35p and the presence of the [PIN] factor.

Conclusions:

• The prionizing peptide of Sup35p is sufficient to induce a [PSI]-like factor when present in a hybrid protein.
• Both the prionizing peptide and the [PIN] factor are essential for de novo induction of the [PSI] factor.
• This study provides insights into the mechanism of prion formation and propagation in Saccharomyces cerevisiae.