A role for A-to-I RNA editing in temperature adaptation

Abstract

A-to-I RNA editing can recode mRNAs, giving organisms the option to express diverse, functionally distinct protein isoforms. Here, we propose that RNA editing is inherently geared for temperature adaptation because it tends to recode to smaller, less stabilizing amino acids. Studies on how editing affects protein function support this idea.

FIGURE 1. Predicted and observed frequencies of codons targeted and created by A-to-I RNA editing

All codons that could be edited to produce a different amino acid were identified. The relative frequencies of these codons in gene coding regions were then determined with the codon usage tables available at http://www.kazusa.or.jp (compiled using sequence data from GenBank, NCBI). Predicted editing percentages were calculated assuming that any adenosine within a codon would be randomly targeted for editing. Observed editing frequencies for Drosophila were based on the 611 sites identified in the developmental transcriptome project (22). For Cephalopods, a list of 79 sites was compiled using published data for Loligo and octopus (11, 18, 35, 49, 52) and also unpublished data from the Rosenthal laboratory. To determine whether the differences between predicted and observed editing frequencies were significant, we calculated the expected standard deviation for sample sizes of 611 and 79. If the observed difference was >2 SD (95% confidence interval) from the expected value, we considered the deviation significant. *Confidence interval of ≥95%. **Confidence interval of ≥99.7%.