Natural human tRNA^Ala anticodon variants mistranslate the genetic code

Area of Science:

• Molecular Biology
• Genetics

Background:

• Transfer RNAs (tRNAs) are crucial for protein synthesis, translating genetic code.
• Human genomes contain over 400 tRNA genes with population-level single-nucleotide polymorphisms, including anticodon variants.
• Anticodon variants can lead to mistranslation, altering the protein sequence.

Purpose of the Study:

• To investigate the functional impact of naturally occurring human alanine tRNA (tRNA^Ala) anticodon variants.
• To determine if these tRNA^Ala variants cause misincorporation of alanine at non-cognate codons.
• To assess the effect of such mistranslation on protein production and cell growth.

Main Methods:

• Identification of three rare human tRNA^Ala variants with anticodon mutations.
• Expression of these variants in human cells.
• Mass spectrometry to quantify amino acid misincorporation.
• Analysis of protein production and cell growth defects.

Main Results:

• Expression of tRNA^Ala variants led to alanine misincorporation at glutamate (0.7%), valine (5%), and threonine (0.1%) codons.
• Despite higher misincorporation at valine codons, alanine misincorporation at glutamate codons caused the most severe protein production defects.
• Cell growth was not substantially impacted by the expression of these variants.

Conclusions:

• Natural human tRNA^Ala variants can induce mistranslation.
• The severity of protein production defects depends on the specific amino acid misincorporated.
• Anticodon mutations in tRNAs represent a source of genetic variation impacting protein synthesis fidelity.