So close yet so far apart: distinct flanking sequence recognition by DNMT3A and DNMT3B

Area of Science:

• Biochemistry
• Molecular Biology
• Epigenetics

Background:

• DNA methyltransferases (DNMTs) are crucial for de novo CpG methylation.
• DNMT3A and DNMT3B are paralogs with similar catalytic domains but distinct biological roles and genomic targeting.
• Understanding their sequence specificity is key to deciphering epigenetic regulation.

Purpose of the Study:

• To elucidate the mechanistic basis for the distinct flanking sequence preferences of DNMT3A and DNMT3B.
• To analyze the atomistic details of base- and shape-readout mechanisms in these enzymes.
• To provide insights into how closely related enzymes achieve divergent substrate recognition.

Main Methods:

• All-atom molecular dynamics (MD) simulations of DNMT3A and DNMT3B complexes.
• Simulations covered 16 microseconds of enzyme-substrate interactions.
• Development and application of a Comparative Dynamics Analysis (CDA) framework.

Main Results:

• DNMT3A exhibits sequence specificity through a rigid hydrogen bonding network and shape-constrained electrostatic anchoring.
• DNMT3B demonstrates broader substrate tolerance via a more flexible and distributed interaction interface.
• The study provides the first systematic analysis of shape readout in DNMT3 enzymes.

Conclusions:

• Flanking sequence specificity in DNMT3 enzymes is dynamically encoded despite high protein similarity.
• Divergent recognition strategies explain the distinct genomic targeting and biological roles of DNMT3A and DNMT3B.
• Findings offer a foundation for engineering paralog-specific protein-DNA interactions.