key term - DNA Methylation

Definition

DNA methylation is an epigenetic modification in which a methyl group is added to the DNA molecule, typically at cytosine residues. This process can influence gene expression without altering the underlying DNA sequence, playing a crucial role in cellular differentiation and development.

5 Must Know Facts For Your Next Test

1. DNA methylation is a key mechanism of epigenetic regulation, influencing gene expression without altering the DNA sequence.
2. Methylation patterns are established and maintained by DNA methyltransferase enzymes, which add methyl groups to cytosine residues.
3. Methylation of gene promoter regions is often associated with transcriptional silencing, while methylation of gene bodies can enhance expression.
4. DNA methylation patterns are crucial for cellular differentiation, as they help establish and maintain cell-specific gene expression programs.
5. Aberrant DNA methylation patterns have been linked to various diseases, including cancer, as they can lead to the inappropriate silencing or activation of genes.

Review Questions

• Explain how DNA methylation is involved in the process of cellular differentiation.
  • During cellular differentiation, specific patterns of DNA methylation are established and maintained, leading to the silencing of genes associated with alternative cell lineages and the activation of genes necessary for the desired cell type. This epigenetic regulation allows for the expression of a unique set of genes that define the identity and function of each specialized cell, despite the fact that all cells in an organism share the same underlying DNA sequence. The establishment and inheritance of these cell-specific methylation patterns are crucial for the proper development and maintenance of different cell types within the body.
• Describe the role of DNA methyltransferase enzymes in the regulation of gene expression through DNA methylation.
  • DNA methyltransferase enzymes are responsible for catalyzing the addition of methyl groups to cytosine residues in the DNA. These enzymes play a critical role in establishing and maintaining DNA methylation patterns throughout the genome. By targeting specific DNA sequences, such as gene promoters, the methyltransferases can induce transcriptional silencing by preventing the binding of transcription factors or recruiting repressive chromatin remodeling complexes. Conversely, methylation of gene bodies can enhance gene expression by facilitating the recruitment of elongation factors. The precise regulation of DNA methyltransferase activity and the resulting methylation patterns are essential for the proper control of gene expression during cellular differentiation and development.
• Analyze how aberrant DNA methylation patterns can contribute to the development of diseases, such as cancer.
  • Disruptions in the normal patterns of DNA methylation have been strongly implicated in the development and progression of various diseases, including cancer. Abnormal hypermethylation of tumor suppressor gene promoters can lead to the silencing of these genes, allowing for uncontrolled cell growth and the evasion of apoptosis - hallmarks of cancer. Conversely, hypomethylation of oncogenes can result in their inappropriate activation, further driving the malignant transformation of cells. Additionally, global changes in DNA methylation patterns can alter the expression of genes involved in genome stability, cell cycle regulation, and other critical cellular processes, contributing to the genomic instability and deregulation characteristic of cancer. Understanding the role of DNA methylation in disease pathogenesis has led to the development of epigenetic-based therapies, which aim to restore the normal methylation landscape and, ultimately, reverse the adverse effects of aberrant DNA methylation.

Related terms

Epigenetics:

The study of heritable changes in gene expression that do not involve changes to the DNA sequence, often influenced by environmental factors.

Cytosine:

One of the four primary nitrogenous bases found in DNA, capable of undergoing methylation.

DNA Demethylation: The removal of methyl groups from DNA, which can reactivate silenced genes and influence cellular processes.