Structural basis for inhibition of DNA replication by aphidicolin

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Aphidicolin is a natural product inhibiting B-family DNA polymerases, crucial for replication and cell division.
• Clinical use of aphidicolin as an antitumor agent is limited by poor solubility and rapid clearance.
• Previous attempts to modify aphidicolin for improved efficacy failed due to lack of structural guidance.

Purpose of the Study:

• To determine the crystal structure of human DNA polymerase alpha (Pol α) in complex with aphidicolin.
• To elucidate the mechanism of aphidicolin's inhibition of Pol α.
• To provide a structural basis for designing improved aphidicolin derivatives.

Main Methods:

• X-ray crystallography was used to determine the structure of the catalytic core of human Pol α.
• The structure was solved for a ternary complex containing the enzyme, an RNA-primed DNA template, and aphidicolin.
• Inhibitory mechanisms were analyzed based on the observed binding interactions.

Main Results:

• The crystal structure reveals aphidicolin bound in the Pol α active site, preventing dCTP binding.
• Aphidicolin induces a conformational change in the template guanine, contributing to its selectivity.
• The structure explains the loss of inhibitory activity in previously synthesized aphidicolin analogs.

Conclusions:

• The determined structure provides critical insights into aphidicolin's mechanism of action and selectivity.
• Aphidicolin serves as a valuable lead compound for developing novel B-family DNA polymerase inhibitors.
• Structural information facilitates the rational design of enhanced anticancer agents based on the aphidicolin scaffold.