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Related Experiment Video

Updated: Feb 6, 2026

Measuring Microbial Mutation Rates with the Fluctuation Assay

Measuring Microbial Mutation Rates with the Fluctuation Assay

Published on: November 28, 2019

Transfer RNA genes experience exceptionally elevated mutation rates.

Bryan P Thornlow¹, Josh Hough¹, Jacquelyn M Roger¹

¹Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064.

Proceedings of the National Academy of Sciences of the United States of America

|August 22, 2018

Summary

This summary is machine-generated.

Transfer RNAs (tRNAs) are vital for protein synthesis. Our study reveals that high transcription rates drive mutations in tRNA genes, but strong selection preserves their function, impacting human health.

Keywords:

TAM computational prediction mutagenesis tRNA transcription

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Area of Science:

Molecular Biology
Evolutionary Biology
Genetics

Background:

Transfer RNAs (tRNAs) are essential for protein synthesis and are highly conserved across species.
The evolutionary pressures shaping tRNA genes remain largely unknown.
Understanding tRNA evolution is crucial for comprehending fundamental cellular processes.

Purpose of the Study:

To investigate the evolutionary forces, specifically transcription-associated mutagenesis and selection, acting on tRNA genes.
To determine the mutation rates and selective pressures at tRNA loci compared to the nuclear genome average.
To explore the relationship between tRNA expression levels and mutation rates in flanking regions.

Main Methods:

Comparative evolutionary analyses of tRNA genes and their flanking sequences in humans and model organisms.
Mutation rate estimation at tRNA loci.
Assessment of purifying selection acting on tRNA genes versus non-coding regions.
Correlation analysis between tRNA expression levels and local mutation rates.

Main Results:

Mutation rates at broadly expressed cytosolic tRNA genes are 7-10 times higher than the nuclear genome average.
Strong purifying selection acts on tRNA genes, counteracting the elevated mutation rate.
A positive correlation exists between tRNA expression levels and mutation rates in adjacent genomic regions.
Mutations at tRNA loci contribute significantly to the overall mutational load.

Conclusions:

Transcription-associated mutagenesis and strong purifying selection are key drivers of tRNA gene evolution.
Elevated mutation rates at tRNA loci have implications for mutational load and fitness in human populations.
The correlation between expression and mutation rate offers a potential method for estimating tRNA gene activity.