5metüültsosiin

5-methylcytosine (5mC) is a modified form of the DNA base cytosine. It is one of the most extensively studied epigenetic modifications in eukaryotes and plays a crucial role in regulating gene expression without altering the underlying DNA sequence. In mammals, 5mC is primarily found in the context of CpG dinucleotides, where a methyl group is attached to the carbon at the fifth position of the cytosine ring. This methylation is catalyzed by DNA methyltransferases (DNMTs).

The presence of 5mC can lead to gene silencing. Methylated DNA can recruit proteins that either physically block transcription factors from binding to the DNA or promote a more condensed chromatin structure, making the DNA inaccessible to the transcriptional machinery. This epigenetic mechanism is vital for various biological processes, including embryonic development, cellular differentiation, and the maintenance of genomic stability. Aberrant DNA methylation patterns are associated with numerous diseases, including cancer, neurological disorders, and autoimmune diseases.

Conversely, demethylation, the removal of the methyl group from cytosine, is also an active process mediated by specific enzymes, allowing for the reactivation of genes. The dynamic interplay between DNA methylation and demethylation is essential for maintaining cellular identity and responding to environmental cues. Research into 5mC and its associated enzymes continues to be a significant area of molecular biology and epigenetics.