MicroRNAs and reactive oxygen species: Are they in the same regulatory circuit?

Here we describe experiments in which changes of ROS and transcript levels are induced by X-irradiation and measured using flow cytometer and the fluorescent dye 2′,7′-dichlorofluorescein diacetate and microarray methods in cultured human K562, Me45 and HCT116 cells. Analysis of the nucleotide sequences of mRNAs which are up- or down-regulated after irradiation shows significant differences in the distributions of miRNA-targeted motives between these two groups. Immediately after irradiation most miRNAs behave as “up-regulators”, showing more targets in up-than in down-regulated transcripts, and this changes about 12 h later when we also observe changes in ROS and miRNA levels. Our results suggest that the changes in the transcriptome could result from changes in RNA interference and that these effects could be related to the changed ROS levels in irradiated cells. We propose that such modulation of gene expression at the mRNA level may be implicated more generally in cellular responses to stresses where ROS levels change.