Which epigenetic modification is commonly associated with gene activation in eukaryotes?

Which epigenetic modification is commonly associated with gene activation in eukaryotes?

• A. Histone acetylation.
• B. DNA methylation.
• C. Histone deacetylation.
• D. RNA methylation.

Answer: (A)

Histone acetylation is the modification most consistently linked to activating gene expression in eukaryotes. When acetyl groups are added to lysine residues on histone tails by histone acetyltransferases, the positive charges on histones are neutralized. This weakens histone-DNA interactions, loosening the nucleosome structure and creating a more open chromatin state (euchromatin). With chromatin loosened, transcription factors and RNA polymerase can access the DNA more easily, promoting transcription. By contrast, DNA methylation at promoters is typically associated with gene silencing, histone deacetylation tightens chromatin and represses transcription, and RNA methylation mainly influences RNA processing and stability rather than directly activating transcription from the DNA. So, histone acetylation stands out as the key modification that promotes gene activation.

Histone acetylation is the modification most consistently linked to activating gene expression in eukaryotes. When acetyl groups are added to lysine residues on histone tails by histone acetyltransferases, the positive charges on histones are neutralized. This weakens histone-DNA interactions, loosening the nucleosome structure and creating a more open chromatin state (euchromatin). With chromatin loosened, transcription factors and RNA polymerase can access the DNA more easily, promoting transcription.

By contrast, DNA methylation at promoters is typically associated with gene silencing, histone deacetylation tightens chromatin and represses transcription, and RNA methylation mainly influences RNA processing and stability rather than directly activating transcription from the DNA. So, histone acetylation stands out as the key modification that promotes gene activation.