Question

What effect does the hypermethylation of promoter regions typically have on gene expression?

• A. Activation of transcription.
• B. Silencing of transcription.
• C. No effect on transcription.
• D. Increased translational efficiency.

Hint:

Remember this simple epigenetic rule: \textbf{Methylation Mutes}. High levels of DNA methylation in a promoter region generally lead to gene silencing. Conversely, demethylation or hypomethylation is associated with gene activation.

Answer 1

The Correct Option is B

Step 1: Concept Overview:
The question concerns DNA methylation's role in gene expression regulation, specifically the impact of promoter hypermethylation.
Step 2: Detailed Explanation:


DNA methylation involves adding a methyl group (-CH₃) to DNA, often at CpG sites.
The promoter, a DNA region where transcription begins, serves as the binding site for RNA polymerase and transcription factors.
Hypermethylation of a gene's promoter silences the gene via two primary mechanisms:

Methyl groups can directly impede transcription factor and RNA polymerase binding, preventing transcription initiation.
Methylated DNA is recognized by methyl-CpG-binding domain proteins (MBDs), which recruit histone deacetylases (HDACs) and other chromatin-remodeling proteins. This results in chromatin compaction into heterochromatin, rendering the gene inaccessible for transcription.

Promoter hypermethylation strongly correlates with transcriptional repression or silencing.
Step 3: Concise Answer:
Hypermethylation of promoter regions typically silences transcription.