Question

How does DNA methylation affect gene expression?

Answer 1

DNA Methylation suppresses gene expression.

Basically, DNA methylation occurs at CpG Islands (CG dinucleotide rich regions found in promoters) and involves the methylation of the fifth Carbon of cytosine to form 5-methyl cytosine (5mC). This acts as a binding site for 5mC binding protein which possesses a histone deacetylation moiety. Deacetylation of histones condenses the DNA restricting the binding of transcription factors. Hence, suppression.

Furthermore, 5mC allows the binding of HeteroChromatin Protein 1 whose size physically inhibits transcription factors from binding to the promoter.

Collectively, methylation suppresses expression.