DNA Methylation and Histone Acetylation || Differences and Similarities

Both DNA methylation and histone modification are epigenetic regulatory mechanisms that influence gene expression without changing the underlying DNA sequence.

Watch our video on this topic: Difference between DNA Methylation & Histone Acetylation

They play crucial roles in gene expression during development, and response to environmental stimulus.

DNA Methylation	Histone Modification
Definition: Addition of a methyl group (CH₃) to the DNA molecule at specific cytosine residues.	The addition of acetyl groups to the lysine residues of the histone proteins (around which DNA wraps)
Location: Occurs directly on the DNA molecule itself.	Takes place on histone proteins within the nucleosome structure.
Causes chromatin condensation.	Causes chromatin relaxation.
Generally, represses gene expression by blocking transcription factors and RNA polymerase.	Generally, activate gene expression, by allowing transcription factors and RNA polymerase to initiate transcription.
DNA methyltransferases catalyze the addition of methyl groups.	Histone acetyltransferases and histone methyltransferases mediate different modifications.
Semi-reversible: Demethylation can occur through active processes.	Reversible: Modifications can be added or removed dynamically.
Example: Gene Silencing in X-Chromosome Inactivation. During embryonic development, one of the X chromosomes in each cell of a female is permanently inactivated primarily by DNA methylation.	Enhancer Activation: Acetylation of K9 and K27 on histone H3 is associated with enhancers and promoters of active genes.

Reference & Image Credit

Vilcinskas, A. (2016). The role of epigenetics in host–parasite coevolution: lessons from the model host insects Galleria mellonella and Tribolium castaneum. Zoology, 119(4), 273-280.