Specific branches of the proteostasis network regulate the toxicity associated with mistranslation

Area of Science:

• Molecular Biology
• Genetics
• Cellular Biology

Background:

• Accurate protein biosynthesis is crucial for all cellular functions.
• Human genomes contain transfer RNA (tRNA) gene variants causing amino acid misincorporation (mistranslation).
• Mistranslation negatively impacts proteostasis, leading to protein misfolding, and impaired synthesis and degradation.

Purpose of the Study:

• To investigate how specific mistranslating tRNA variants interact with proteostasis pathways.
• To quantitatively analyze the effects of distinct mistranslating tRNAs on cellular fitness and protein homeostasis using Saccharomyces cerevisiae.

Main Methods:

• Utilized Saccharomyces cerevisiae (budding yeast) as a model organism for quantitative analysis.
• Tested two mistranslating tRNA Ser variants: proline to serine (P>S) and arginine to serine (R>S) misincorporation.
• Assessed cellular fitness, protein misfolding, and proteostasis pathway interactions.

Main Results:

• P>S misincorporation impaired cellular fitness and increased sensitivity to protein misfolding more than R>S.
• Both tRNA variants caused serine misincorporation but affected protein accumulation via different mechanisms.
• R>S misincorporation reduced Hsp70 association with misfolded proteins; P>S impaired nascent polypeptide degradation.

Conclusions:

• Different mistranslating tRNA variants uniquely disrupt specific proteostasis branches.
• The distinct mechanisms of proteostasis impairment by mistranslating tRNAs compromise cellular fitness.
• Understanding these mechanisms is vital for comprehending genetic variant impacts on cellular health.