Minimalist model for force-dependent DNA replication.

Area of Science:

• Biophysics
• Molecular Biology
• Biochemistry

Background:

• Polymerase enzymes catalyze DNA replication, a process sensitive to mechanical forces.
• Previous studies used optical/magnetic tweezers and molecular dynamics (MD) simulations to investigate force-dependent replication rates.

Purpose of the Study:

• To develop a simple, predictive model for DNA polymerase replication rate dependence on tension.
• To understand the structural basis for force-induced changes in enzyme activity.

Main Methods:

• Development of a minimalist two-segment local (M2L) model based on MD simulations of Taq polymerase.
• Utilizing structural data and a critical tension parameter (f*) to predict replication rate.
• Applying the M2L model to various polymerases, including Family A, Family B, and HIV reverse transcriptase.

Main Results:

• The M2L model successfully predicts the observed tension dependence of replication rates for different polymerases.
• A critical tension (f*) was identified, at which a DNA segment reorients significantly in the enzyme's open conformation.
• The model accounts for replication rate changes based on enthalpy changes in DNA segments near the nucleotide addition site.

Conclusions:

• The M2L model provides a simplified yet effective framework for understanding force-dependent DNA replication.
• Structural rearrangements, particularly at the critical tension f*, are key determinants of polymerase activity under force.
• The model offers insights into DNA repair and replication mechanisms influenced by mechanical stress.