tRNA-modifying enzyme mutations induce codon-specific mistranslation and protein aggregation in yeast.

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Protein synthesis accuracy and co-translational folding are vital for proteome homeostasis.
• The precise roles of mRNA translational factors in maintaining protein synthesis fidelity remain incompletely understood.

Purpose of the Study:

• To investigate the role of tRNA-modifying enzymes in preventing protein aggregation and maintaining proteostasis.
• To identify aggregated proteins and understand the impact of specific tRNA modifications on protein synthesis accuracy.

Main Methods:

• Screened 70 yeast tRNA-modifying enzyme genes for their impact on protein aggregation.
• Utilized mass spectrometry to identify proteins accumulating in aggregates.
• Analyzed amino acid misincorporation rates in knockout strains.

Main Results:

• Specific tRNA modifications at uridine at anticodon position 34 (U34) by Elp1, Elp3, Sml3, and Trm9 are critical for proteostasis.
• The mitochondrial tRNA-modifying enzyme Slm3 is essential for general proteostasis.
• Stress response proteins decoded by tRNAs lacking specific U34 modifications (mcm5U34, mcm5s2U34, ncm5U34, ncm5Um34) were overrepresented in aggregates in knockout strains.
• Increased amino acid misincorporation occurred at sites decoded by hypomodified tRNAs in knockout strains.

Conclusions:

• U34 tRNA modifications are essential for safeguarding the proteome against translational errors and protein misfolding.
• Deficiencies in U34 tRNA modifications lead to protein aggregation and proteotoxic stress.
• These findings highlight the critical role of tRNA modification in maintaining cellular proteostasis.