Gadd45a promotes epigenetic gene activation by repair-mediated DNA demethylation

• Published in: Nature 2007-02, Vol.445 (7128), p.671-675
• Main Authors: Maltry, Nicole, Marhold, Joachim, Döderlein, Gabi, Barreto, Guillermo, Wu, Wei, Niehrs, Christof, Handa, Vikas, Swaminathan, Suresh K, Schäfer, Andrea, Stach, Dirk, Lyko, Frank
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cell Line; Cloning, Molecular; Deoxyribonucleic acid; DNA; DNA Methylation; DNA Repair; Epigenesis, Genetic; Freshwater; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Silencing; Genes, Reporter - genetics; Genomics; Humanities and Social Sciences; Humans; letter; Life Sciences; Mice; Molecular and cellular biology; Molecular biology; Molecular genetics; multidisciplinary; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Octamer Transcription Factor-3 - genetics; Octamer Transcription Factor-3 - metabolism; Oocytes - metabolism; Promoter Regions, Genetic - genetics; Proteins; Science; Science (multidisciplinary); Substrate Specificity; Transcription. Transcription factor. Splicing. Rna processing; Up-Regulation - genetics; Xenopus - genetics; Xenopus - metabolism; Xenopus laevis; Xenopus Proteins - genetics; Xenopus Proteins - metabolism
• ISSN: 0028-0836; 1476-4687; 1476-4679
• DOI: 10.1038/nature05515

DNA methylation is an epigenetic modification that is essential for gene silencing and genome stability in many organisms. Although methyltransferases that promote DNA methylation are well characterized, the molecular mechanism underlying active DNA demethylation is poorly understood and controversial. Here we show that Gadd45a (growth arrest and DNA-damage-inducible protein 45 alpha), a nuclear protein involved in maintenance of genomic stability, DNA repair and suppression of cell growth, has a key role in active DNA demethylation. Gadd45a overexpression activates methylation-silenced reporter plasmids and promotes global DNA demethylation. Gadd45a knockdown silences gene expression and leads to DNA hypermethylation. During active demethylation of oct4 in Xenopus laevis oocytes, Gadd45a is specifically recruited to the site of demethylation. Active demethylation occurs by DNA repair and Gadd45a interacts with and requires the DNA repair endonuclease XPG. We conclude that Gadd45a relieves epigenetic gene silencing by promoting DNA repair, which erases methylation marks.