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Methylation of DNA, RNA and proteins (notably histones) is one of the most ubiquitous and dynamic chemical modifications in eukaryotes, and has great impact on gene expression and protein function. The importance of methylation is evidenced by the diseases associated with its dysregulation, including cancer and immunological and neurological disorders. The Reviews in this focus issue showcase the latest understanding of the mechanisms and roles of methylation in animals and its clinical relevance.
N6-methyladenosine (m6A) is the most abundant mRNA internal modification. The recent mapping of m6A has provided insights into which and how mRNAs are modified, how m6A affects gene expression and how it is linked to cellular differentiation, cancer progression and other biological processes.
DNA methylation is essential for mammalian embryogenesis owing to its repression of transposons and genes, but it is also associated with gene activation. The recent use of sensitive technologies has revealed that DNA methylation dynamics vary considerably between embryonic, germline and somatic cell development, with implications for genetic diseases and cancer.
The methylation of arginine residues regulates gene expression, DNA repair, growth factor signalling and liquid–liquid phase separation. Targeting this modification can thus be therapeutically relevant and inhibitors of arginine methylation are being tested in clinical trials, especially for neurodegenerative diseases and cancer.
The dynamic methylation of chromatin components — DNA, histones and RNA — is crucial in development, ageing and cancer. Therapies that target regulators of DNA and histone methylation in cancer have recently been developed. These promising therapies, which include strategies that may improve tumour immune surveillance, are already being tested in early-phase clinical trials.
Histone methylation regulates gene expression throughout animal development, governing processes as diverse as cell fate decisions, lineage specification, body patterning and organogenesis. Better understanding of the complex, context-specific roles of histone methylation in development will shed new light on the aetiology of developmental disorders.