Differential dynamics specify MeCP2 function at methylated DNA and nucleosomes.

Area of Science:

• Epigenetics and Molecular Biology
• Biophysics of DNA-protein interactions

Background:

• Methyl-CpG-binding protein 2 (MeCP2) is crucial for neurodevelopment; mutations cause Rett syndrome (RTT), a primary genetic intellectual disability in females.
• The precise mechanisms governing MeCP2's interaction with chromatin and its role in gene regulation are not fully understood.

Approach:

• Employed correlative single-molecule fluorescence and force microscopy to directly observe MeCP2 behavior on DNA and chromatin substrates.
• Investigated MeCP2's diffusion dynamics on methylated and unmethylated DNA, as well as its interaction with nucleosomes.

Key Points:

• MeCP2 displays distinct diffusion dynamics on unmethylated versus methylated DNA.
• MeCP2 preferentially binds to nucleosomes within chromatin, enhancing their stability against mechanical stress.
• MeCP2's differential binding behavior dictates its recruitment of the TBLR1 co-repressor component.

Conclusions:

• RTT-associated mutations impair specific MeCP2-chromatin interactions, correlating with disease variability.
• Findings support a nucleosome-centric model for MeCP2's genomic distribution and gene repression.
• This study elucidates the biophysical underpinnings of MeCP2's methylation-dependent functions and RTT pathogenesis.