The machinery involved in the RNA interference (RNAi) pathway may protect genomes against some accidental changes in how DNA is chemically modified, geneticists have found.
Modifying DNA by adding methyl groups is a common way in which cells silence certain genes, but methylation can erode over time, making the silencing less effective.
Vincent Colot at the École Normale Supérieure in Paris and his colleagues studied Arabidopsis thaliana mutants that have reduced DNA methylation throughout the genome. They crossed these mutants with normal plants and found that methylation gradually returned to some genes in offspring that no longer carried the mutation. Previous research had shown that methylation doesn't return once lost. Sites that were remethylated complemented the sequence of small RNA molecules that are involved in RNAi; methylation was not restored in mutants that did not make these RNAs.
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Molecular biology: RNA repair. Nature 457, 639 (2009). https://doi.org/10.1038/457639a
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DOI: https://doi.org/10.1038/457639a
