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Antioxid Redox Signal. 2018 Jan 1;28(1):62-77. doi: 10.1089/ars.2016.6871. Epub 2017 May 1.

A Peroxidase Peroxiredoxin 1-Specific Redox Regulation of the Novel FOXO3 microRNA Target let-7.

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1 Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh , Pittsburgh, Pennsylvania.
2 Department of Pharmacology and Chemical Biology, Magee Womens Research Institute, University of Pittsburgh Cancer Institute , Pittsburgh, Pennsylvania.
3 Department of Pathology, Harvard Medical School and Beth Israel Deaconess Medical Center , Boston, Massachusetts.
4 Oncogenomic and Epigenetic Unit, Department of Research, Advanced Diagnostics and Technological Innovation, Translational Research Area Regina Elena National Cancer Institute , Rome, Italy .
5 Department of Pharmaceutical Sciences, University of Pittsburgh , Pittsburgh, Pennsylvania.
6 Institute of Biochemistry of the Romanian Academy, Bucharest, Romania .


Precision in redox signaling is attained through posttranslational protein modifications such as oxidation of protein thiols. The peroxidase peroxiredoxin 1 (PRDX1) regulates signal transduction through changes in thiol oxidation of its cysteines. We demonstrate here that PRDX1 is a binding partner for the tumor suppressive transcription factor FOXO3 that directly regulates the FOXO3 stress response. Heightened oxidative stress evokes formation of disulfide-bound heterotrimers linking dimeric PRDX1 to monomeric FOXO3. Absence of PRDX1 enhances FOXO3 nuclear localization and transcription that are dependent on the presence of Cys31 or Cys150 within FOXO3. Notably, FOXO3-T32 phosphorylation is constitutively enhanced in these mutants, but nuclear translocation of mutant FOXO3 is restored with PI3K inhibition. Here we show that on H2O2 exposure, transcription of tumor suppressive miRNAs let-7b and let-7c is regulated by FOXO3 or PRDX1 expression levels and that let-7c is a novel target for FOXO3. Conjointly, inhibition of let-7 microRNAs increases let-7-phenotypes in PRDX1-deficient breast cancer cells. Altogether, these data ascertain the existence of an H2O2-sensitive PRDX1-FOXO3 signaling axis that fine tunes FOXO3 activity toward the transcription of gene targets in response to oxidative stress. Antioxid. Redox Signal. 28, 62-77.


FOXO3; PRDX1; breast cancer; let-7; oxidative stress; tumor suppressor

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