Abstract
Errors that occur during transcription have received much less attention than the mutations that occur in DNA because transcription errors are not heritable and usually result in a very limited number of altered proteins. However, transcription error rates are typically several orders of magnitude higher than the mutation rate. Also, individual transcripts can be translated multiple times, so a single error can have substantial effects on the pool of proteins. Transcription errors can also contribute to cellular noise, thereby influencing cell survival under stressful conditions, such as starvation or antibiotic stress. Implementing a method that captures transcription errors genome-wide, we measured the rates and spectra of transcription errors in Escherichia coli and in endosymbionts for which mutation and/or substitution rates are greatly elevated over those of E. coli Under all tested conditions, across all species, and even for different categories of RNA sequences (mRNA and rRNAs), there were no significant differences in rates of transcription errors, which ranged from 2.3 × 10(-5) per nucleotide in mRNA of the endosymbiont Buchnera aphidicola to 5.2 × 10(-5) per nucleotide in rRNA of the endosymbiont Carsonella ruddii The similarity of transcription error rates in these bacterial endosymbionts to that in E. coli (4.63 × 10(-5) per nucleotide) is all the more surprising given that genomic erosion has resulted in the loss of transcription fidelity factors in both Buchnera and Carsonella.
Highlights
The authors note wish to note the following: “While compiling our transcription error rate data for distribution, we discovered that a fraction of errors went unreported
Across all species, and even for different categories of RNA sequences, there were no significant differences in rates of transcription errors, which ranged from 2.3 × 10−5 per nucleotide in mRNA of the endosymbiont Buchnera aphidicola to 5.2 × 10−5 per nucleotide in rRNA of the endosymbiont Carsonella ruddii
By assessing the transcription errors genomewide in Escherichia coli and in two bacterial endosymbionts, we discovered that all species had remarkably similar transcription error rates
Summary
The authors note wish to note the following: “While compiling our transcription error rate data for distribution, we discovered that a fraction of errors went unreported. “In our original report, we were testing the hypothesis that the bacterial endosymbionts Buchnera and Carsonella, which have higher DNA substitution rates than E. coli, have increased rates of transcription errors. Estimates of the rate of transcription errors in Escherichia coli have been determined in vitro by measuring the misincorporation of radiolabeled nucleotides into repeating dinucleotide tracts [1, 9] and in vivo by quantifying the reversion frequencies of nonsense mutations in lacZ [2, 3] These assays yielded variable estimates of transcription error rates of 10−4–10−5 per nucleotide, several orders of magnitude higher than the mutation rate [10,11,12]. Transcription error rate reversion assays based on the recovery of functional proteins might include translation errors, if these occur at a sufficiently high rate
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