 The regulatory mechanisms by which hydrogen peroxide H2O2 modulates the activity of transcription factors in different organisms are reviewed. H2O2 triggers multiple sensors and pathways that converge in the regulation of transcription factors at several levels, including synthesis, stability, cytoplasm nuclear traffic, DNA binding, and nuclear transactivation. The complexity of regulatory networks increases throughout the phylogenetic tree, with mammalians having a high level of complexity. H2O2 biological specificity results from diverse-style protein sensors with different reactivity towards H2O2 and localized production and removal controlled by signals. Quantitative data concerning H2O2 reactivity with sensor molecules can be extracted from typical experiments with rate constants estimated for the reaction of H2O2 with KAP1 and an unknown target that mediates an RF2 protein synthesis. The multitude of H2O2 targets and mechanisms provides an opportunity for highly specific effects on gene regulation that depend on the cell type and signals received from the cellular microenvironment. This article was authored by H. Susanna Marineho, Carla Reel, Louisa Cern and others. We are article.tv, links in the description below.