DNA methylation is a heritable epigenetic mark in which DNA methyltransferases (DNMTs) covalently transfer a methyl group to the C-5 position of the DNA cytosine ring. Cytosines are methylated in plants either in symmetrical circumstances (CG or CHG) or in asymmetrical contexts (CHH, where H is A, T, or C). Gene expression can alter in heritable ways that the DNA sequence does not encode. Characterising epigenetic modifications throughout healthy development and in disease states like cancer has advanced significantly in the last ten years. The epigenetic landscape, which includes DNA methylation, the histone code, non-coding RNA, and nucleosome placement, has become more complex sequence (Obembe et al., 2015). DNA methylation, which the DNA methyltransferases (DNMTs) catalyse, is recognised as a crucial factor in the epigenetic silencing of transcription because it serves as a persistent restrictive mark. Through the interaction of DNMTs with other modifications and with elements of the machinery mediating those marks, DNA methylation may cooperatively control the chromatin state. The relationships between DNA methylation and other epigenetic markers will be thoroughly discussed in this review, along with the molecular processes of transcriptional repression in development and cancer.
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