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Definition: How does DNA methylation affect chromatin structure?

DNA methylation is a process by which a methyl group is added to the DNA molecule, specifically to the cytosine residue of a CpG dinucleotide. This modification plays a crucial role in regulating gene expression and maintaining genome stability.

Effects of DNA Methylation on Chromatin Structure

1. Gene Silencing: DNA methylation is often associated with gene silencing, particularly when it occurs in the promoter region of a gene. Methylated DNA attracts proteins called methyl-binding domain proteins, which recruit other proteins that modify the chromatin structure. These modifications lead to a condensed chromatin state known as heterochromatin, making the gene inaccessible to transcription factors and RNA polymerase, effectively silencing its expression.

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2. Chromatin Remodeling: DNA methylation can also influence chromatin structure by recruiting chromatin remodeling complexes. These complexes alter the positioning of nucleosomes along the DNA, resulting in changes in chromatin accessibility. Methylation-dependent chromatin remodeling can either promote or inhibit gene expression, depending on the specific context and the presence of other regulatory factors.

3. DNA Replication and Repair: DNA methylation patterns are faithfully maintained during DNA replication through a process called maintenance methylation. This process involves the recruitment of DNA methyltransferases to the newly synthesized DNA strand, which adds methyl groups to the corresponding CpG sites. By preserving the methylation patterns, chromatin structure and gene expression patterns can be inherited across cell divisions. Additionally, DNA methylation can also influence DNA repair processes by recruiting proteins involved in DNA damage response and repair pathways.

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4. Epigenetic Memory: DNA methylation can serve as an epigenetic memory mechanism, allowing cells to remember past developmental or environmental cues. During development, DNA methylation patterns undergo dynamic changes, and these changes can be transmitted to daughter cells, influencing their gene expression profiles and cell fate decisions. This epigenetic memory is crucial for maintaining cell identity and tissue-specific gene expression patterns.

In summary, DNA methylation plays a significant role in shaping chromatin structure. It can lead to gene silencing, chromatin remodeling, preservation of DNA methylation patterns during replication, and establishment of epigenetic memory. These effects contribute to the regulation of gene expression and maintenance of genome stability.

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Keywords: methylation, chromatin, expression, structure, patterns, silencing, proteins, remodeling, epigenetic