Differential repair enzyme-substrate selection within dynamic DNA energy landscapes

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• DNA triplet repeats form dynamic, bulged-loop structures.
• Abasic sites are common DNA lesions that can disrupt DNA structure.
• The APE1 enzyme is crucial for DNA repair, particularly base excision repair.

Purpose of the Study:

• To investigate how abasic sites influence the DNA energy landscape and APE1 enzyme repair outcomes.
• To understand the role of structural context in abasic site recognition and repair.
• To explore the impact of DNA dynamic redistribution on enzymatic processing.

Main Methods:

• Employing kinetic trapping to monitor DNA bulge loop states.
• Utilizing enzymatic digestions and biophysical characterizations.
• Analyzing DNA substrate redistribution under enzymatic influence.

Main Results:

• Abasic sites alter the dynamic energy landscape of DNA triplet repeats, affecting APE1 repair.
• APE1 enzyme activity induces redistribution of DNA states from kinetically trapped to equilibrium distributions.
• The equilibrium distribution contains non-viable substrate states for APE1, reducing available substrates.

Conclusions:

• APE1 activity can lead to enzymatic self-repression by inducing thermodynamically optimal but non-substrate DNA states.
• This mechanism impacts DNA repair efficiency within dynamic landscapes, potentially slowing or misdirecting repair.
• Understanding these dynamics is crucial for DNA regulation and repair pathway fidelity.