DNSmetilekció

DNSmetilekció, or DNA methylation in English, is a biochemical process in which a methyl group is added to the 5 position of cytosine residues in DNA, most commonly at CpG dinucleotides. This epigenetic modification is carried out by DNA methyltransferases, including maintenance DNMT1 and de novo DNMT3A and DNMT3B in humans. Methylation patterns are established during development and are propagated through cell divisions, contributing to the stable regulation of gene expression.

Methylation influences gene activity through chromatin and transcriptional changes. When occurring in gene promoters, methylation typically represses transcription by hindering transcription factor binding and recruiting proteins that promote a closed chromatin state. Methylation within gene bodies can correlate with active transcription, highlighting that the effect of methylation depends on genomic context. Global patterns are tissue- and development-specific and include features such as CpG islands, regions with high CpG density often unmethylated in promoters.

Abnormal DNA methylation is linked to numerous diseases and physiological processes. In cancer, promoter hypermethylation can silence tumor suppressor genes, while global hypomethylation can contribute to genomic instability. Aberrant methylation is also involved in imprinting disorders, X-chromosome inactivation, aging, and responses to environmental factors.

Removal and remodeling of methylation occur through active demethylation, involving enzymes such as TET proteins that oxidize 5-methylcytosine, as well as passive demethylation during DNA replication without maintenance methylation.

Techniques to study DNSmetilekció include bisulfite sequencing, methylation-specific PCR, array-based profiling, and whole-genome bisulfite sequencing, enabling mapping and quantification of methylation patterns across the genome.