Final answer:
DNA methyltransferase generally inhibits gene expression by adding methyl groups to DNA, leading to a more condensed chromatin structure and reduced access for the transcription machinery. Drugs that reduce DNA methylation can reactivate silenced genes in cancer cells, offering a therapeutic strategy for cancer treatment.
Step-by-step explanation:
DNA methyltransferase is an enzyme involved in the epigenetic regulation of gene expression in eukaryotic cells. Methylation of cytosine bases in DNA, primarily at CpG dinucleotides, by DNA methyltransferase generally suppresses gene expression. This enzymatic activity adds methyl groups to the DNA molecule, altering the interaction between DNA and transcription factors. These modifications can lead to a more condensed chromatin structure, which makes the DNA less accessible for transcription machinery, thus inhibiting gene expression.
Drugs that decrease DNA methylation are being developed to make DNA more accessible, thereby activating gene expression. This approach can be used in cancer treatment because tumor suppressor genes often become hypermethylated and silenced in cancer cells. By reducing methylation levels, these genes can be reactivated, potentially slowing down or stopping the growth of cancer cells.