DNA methylation, nucleic acid structure, and rett mutations tune MeCP2 binding affinity and cooperativity.

Area of Science:

• Molecular Biology
• Genetics
• Epigenetics

Background:

• Methyl-CpG-binding protein 2 (MeCP2) is crucial for chromatin regulation.
• MeCP2 dysfunction leads to Rett syndrome, a neurodevelopmental disorder.
• MeCP2's selective DNA binding mechanism, despite low affinity for methylated DNA, remains unclear.

Purpose of the Study:

• To investigate the binding characteristics of wild-type and Rett-associated MeCP2 variants to diverse nucleic acid substrates.
• To elucidate how MeCP2 distinguishes methylated from unmethylated DNA.
• To understand the mechanistic basis of Rett syndrome-associated mutations in MeCP2.

Main Methods:

• Quantitative analysis of full-length wild-type and mutant MeCP2 binding affinities.
• Testing interactions with nucleic acid substrates varying in length, structure, methylation, and composition.
• Characterizing binding modes influenced by methylation and nucleic acid topology.

Main Results:

• MeCP2 binds double-stranded DNA preferentially but also interacts with single-stranded DNA/RNA with nanomolar affinity.
• 5-methylcytosine stabilizes MeCP2 binding, particularly when canonical duplex geometry is absent.
• Rett-associated mutations were classified: methyl-binding domain mutations reduced affinity, while C-terminal mutations impaired cooperative interactions.

Conclusions:

• MeCP2 functions as a methyl-sensitive nucleic acid binder, with interactions modulated by cytosine methylation and nucleic acid topology.
• Distinct classes of Rett syndrome mutations differentially disrupt MeCP2's DNA binding and chromatin regulatory functions.
• Findings provide a mechanistic framework for MeCP2 dysfunction in Rett syndrome.