RESUMO
DNA hydroxylation catalyzed by Tet dioxygenases occurs abundantly in embryonic stem cells and neurons in mammals. However, its biological function in vivo is largely unknown. Here, we demonstrate that Tet1 plays an important role in regulating neural progenitor cell proliferation in adult mouse brain. Mice lacking Tet1 exhibit impaired hippocampal neurogenesis accompanied by poor learning and memory. In adult neural progenitor cells deficient in Tet1, a cohort of genes involved in progenitor proliferation were hypermethylated and downregulated. Our results indicate that Tet1 is positively involved in the epigenetic regulation of neural progenitor cell proliferation in the adult brain.
Assuntos
Envelhecimento/metabolismo , Cognição , Proteínas de Ligação a DNA/metabolismo , Hipocampo/crescimento & desenvolvimento , Hipocampo/metabolismo , Neurogênese , Proteínas Proto-Oncogênicas/metabolismo , Animais , Proliferação de Células , Metilação de DNA/genética , Proteínas de Ligação a DNA/deficiência , Giro Denteado/citologia , Regulação da Expressão Gênica , Proteínas de Fluorescência Verde/metabolismo , Memória , Camundongos , Nestina/metabolismo , Neurogênese/genética , Neurônios/citologia , Neurônios/metabolismo , Regiões Promotoras Genéticas/genética , Proteínas Proto-Oncogênicas/deficiência , Células-Tronco/citologia , Células-Tronco/metabolismoRESUMO
Cytosine methylation of genomic DNA controls gene expression and maintains genome stability. How a specific DNA sequence is targeted for methylation by a methyltransferase is largely unknown. Here, we show that histone H3 tails lacking lysine 4 (K4) methylation function as an allosteric activator for methyltransferase Dnmt3a by binding to its plant homeodomain (PHD). In vitro, histone H3 peptides stimulated the methylation activity of Dnmt3a up to 8-fold, in a manner reversely correlated with the level of K4 methylation. The biological significance of allosteric regulation was manifested by molecular modeling and identification of key residues in both the PHD and the catalytic domain of Dnmt3a whose mutations impaired the stimulation of methylation activity by H3 peptides but not the binding of H3 peptides. Significantly, these mutant Dnmt3a proteins were almost inactive in DNA methylation when expressed in mouse embryonic stem cells while their recruitment to genomic targets was unaltered. We therefore propose a two-step mechanism for de novo DNA methylation - first recruitment of the methyltransferase probably assisted by a chromatin- or DNA-binding factor, and then allosteric activation depending on the interaction between Dnmt3a and the histone tails - the latter might serve as a checkpoint for the methylation activity.
