RESUMO
Adenine N6 methylation in DNA (6mA) is widespread among bacteria and phage and is detected in mammalian genomes, where its function is largely unexplored. Here we show that 6mA deposition and removal are catalyzed by the Mettl4 methyltransferase and Alkbh4 dioxygenase, respectively, and that 6mA accumulation in genic elements corresponds with transcriptional silencing. Inactivation of murine Mettl4 depletes 6mA and causes sublethality and craniofacial dysmorphism in incross progeny. We identify distinct 6mA sensor domains of prokaryotic origin within the MPND deubiquitinase and ASXL1, a component of the Polycomb repressive deubiquitinase (PR-DUB) complex, both of which act to remove monoubiquitin from histone H2A (H2A-K119Ub), a repressive mark. Deposition of 6mA by Mettl4 triggers the proteolytic destruction of both sensor proteins, preserving genome-wide H2A-K119Ub levels. Expression of the bacterial 6mA methyltransferase Dam, in contrast, fails to destroy either sensor. These findings uncover a native, adversarial 6mA network architecture that preserves Polycomb silencing.
Assuntos
Adenina/análogos & derivados , Homólogo AlkB 4 da Lisina Desmetilase/genética , Anormalidades Craniofaciais/genética , DNA/genética , Metiltransferases/genética , Proteínas Repressoras/genética , Adenina/metabolismo , Homólogo AlkB 4 da Lisina Desmetilase/metabolismo , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Anormalidades Craniofaciais/metabolismo , Anormalidades Craniofaciais/patologia , DNA/metabolismo , Metilação de DNA , Enzimas Desubiquitinantes/genética , Enzimas Desubiquitinantes/metabolismo , Feminino , Inativação Gênica , Genes Letais , Histonas/genética , Histonas/metabolismo , Endogamia , Masculino , Metiltransferases/deficiência , Camundongos , Camundongos Knockout , Proteólise , Proteínas Repressoras/metabolismo , Transdução de Sinais , DNA Metiltransferases Sítio Específica (Adenina-Específica)/genética , DNA Metiltransferases Sítio Específica (Adenina-Específica)/metabolismo , Transcrição Gênica , Ubiquitina/genética , Ubiquitina/metabolismoRESUMO
ALKBH4 is a versatile demethylase capable of catalyzing the demethylation of monomethylated lysine-84 on actin and N6 -methyladenine in DNA. In this study, we conducted a quantitative proteomic experiment to reveal the altered expression of proteins in HEK293T cells upon genetic ablation of ALKBH4. Our results showed markedly diminished levels of GSTP1 and HSPB1 proteins in ALKBH4-depleted cells, which emanate from an augmented expression level of DNA (cytosine-5)-methyltransferase 1 (DNMT1) and the ensuing elevated cytosine methylation in the promoter regions of GSTP1 and HSPB1 genes. Together, our results revealed a role of ALKBH4 in modulating DNA cytosine methylation through regulating the expression level of DNMT1 protein.