DNSmetiláció

DNS methylation is a fundamental epigenetic mechanism that plays a crucial role in gene regulation and cellular processes. It involves the addition of a methyl group to a cytosine base, most commonly occurring at CpG dinucleotides, where a cytosine is followed by a guanine. This biochemical modification does not alter the DNA sequence itself but can significantly influence gene expression.

In mammals, DNA methylation is primarily carried out by DNA methyltransferases (DNMTs), which can be categorized into de novo methyltransferases (DNMT3A and DNMT3B) responsible for establishing new methylation patterns, and maintenance methyltransferases (DNMT1) that copy existing patterns during DNA replication. The methyl group is typically added to the 5th carbon of the cytosine ring, resulting in 5-methylcytosine (5mC).

The impact of DNA methylation on gene expression is context-dependent. Generally, methylation in promoter regions, especially within CpG islands (regions rich in CpG dinucleotides), is associated with gene silencing. This is because the presence of 5mC can interfere with the binding of transcription factors or recruit methyl-CpG-binding domain (MBD) proteins, which in turn recruit repressor complexes. Conversely, methylation in gene bodies can sometimes be associated with gene activation or have no effect.

DNA methylation is involved in a wide array of biological processes, including embryonic development, X-chromosome inactivation, genomic imprinting, and the suppression of transposable elements. Aberrant DNA methylation patterns are implicated in various diseases, most notably cancer, where hypermethylation of tumor suppressor gene promoters can lead to their silencing, contributing to uncontrolled cell growth. Understanding DNA methylation is vital for comprehending normal cellular function and developing strategies for disease intervention.