An epigenetic gene regulation mechanism that negatively regulates gene expression by methylation of cytosine residues in chromosomal CpG islands. CpG islands are genomic regions that contain a high frequency of the CG dinucleotide associated with the transcription start site of genes.
An epigenetic gene regulation mechanism that positively regulates gene expression by demethylation of cytosine residues in chromosomal CpG islands. CpG islands are genomic regions that contain a high frequency of the CG dinucleotide and are often associated with the transcription start site of genes.
An epigenetic cytosine DNA demethylation pathway that involves a DNA glycosylase that directly excises 5-methylcytosine (5-meC) to initiate its replacement with unmethylated cytosine through base excision repair. This pathway is known to occur in plants. In addition to CG sites, plants also methylate cytosines within CHH and CNG sequences.