5metüültsütosiiniks

5-methylcytosine is a modified form of the DNA base cytosine. It is the most common epigenetic modification in eukaryotes. In this modification, a methyl group is attached to the carbon atom at the fifth position of the cytosine ring. This process is called DNA methylation. The enzyme responsible for adding the methyl group is DNA methyltransferase. 5-methylcytosine plays a crucial role in regulating gene expression. It is often found in CpG islands, which are regions of DNA with a high frequency of cytosine and guanine nucleotides. When 5-methylcytosine occurs within a gene promoter, it typically leads to gene silencing. This occurs through a variety of mechanisms, including blocking the binding of transcription factors to DNA or recruiting proteins that condense chromatin, making the DNA less accessible for transcription. The pattern of DNA methylation is dynamic and can change during development, in response to environmental factors, and in various disease states, including cancer. Demethylation, the removal of the methyl group, can also occur, leading to gene activation. The study of 5-methylcytosine and its role in gene regulation is a significant area of epigenetics research.