Final answer:
CpG dinucleotides are prone to mutations that regulate transcription by altering how DNA interacts with proteins; methylation at these sites can lead to gene silencing and play a role in diseases such as cancer.
Step-by-step explanation:
CpG dinucleotides are regions of DNA where a cytosine nucleotide is followed by a guanine nucleotide in the linear sequence of bases along its 5' → 3' direction. These dinucleotides are often found in promoter regions of genes and are prone to mutation due to deamination of methyl cytosine to thymine, making them hotspots for mutation. The methylation of cytosine in CpG islands can regulate transcription by changing how DNA interacts with proteins, like the histone proteins that control access to the DNA, and thereby affecting gene expression.
Gene regulation in eukaryotes involves multiple transcription factors and cofactors that respond to various signals and bind to different regulatory DNA sequences including the CpG islands. Transcription factors can either activate or repress gene expression by interacting with these regulatory sequences. Methylation of CpG sites is an epigenetic mechanism that can silence genes and play a role in the development of diseases like cancer by altering gene expression. In cancer, mutations might increase the binding of transcription factors to promoter regions or enhancers, leading to abnormal gene expression and unchecked cell growth.