Epigenetic CpG duplex marks probed by an evolved DNA reader via a well-tempered conformational plasticity.

Area of Science:

• Epigenetics and Molecular Biology
• Structural Biology
• Biochemistry

Background:

• 5-methylcytosine (mC) and its oxidized derivatives are crucial epigenetic marks in mammalian DNA.
• The regulatory roles of specific combinations of these marks within CpG dyads across DNA strands are not well understood.
• Developing molecular tools to recognize these 'CpG duplex marks' is essential for biological studies.

Purpose of the Study:

• To investigate the design principles for creating selective readers of oxidized CpG duplex marks.
• To understand how molecular recognition of these novel DNA modifications can be achieved.

Main Methods:

• Directed evolution was used to engineer a novel DNA-binding protein scaffold.
• Mutational studies were employed to probe structure-function relationships.
• Nuclear Magnetic Resonance (NMR) relaxation and Molecular Dynamics (MD) simulations were utilized to analyze molecular interactions and dynamics.

Main Results:

• The study identified the first designer reader capable of selectively recognizing an oxidized CpG duplex mark.
• Selectivity was found to depend critically on the conformational plasticity of the reader scaffold, fine-tuned during evolution.
• Defined motional features of the reader are crucial for achieving high affinity and specificity in DNA/protein interactions.

Conclusions:

• The design of selective readers for novel DNA epigenetic marks is feasible.
• Molecular dynamics and conformational flexibility are key factors in the design of high-affinity DNA-binding proteins.
• This work opens new avenues for developing tools to study DNA epigenetic regulation and DNA recognition.