Carcinogenic adducts induce distinct DNA polymerase binding orientations

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• DNA polymerases are crucial for accurate DNA replication and genome integrity.
• Carcinogenic adducts, including 2-aminofluorene (AF) and N-acetyl-2-aminofluorene (AAF), can form covalent bonds with DNA bases.
• These adducts are known to promote mutagenesis, but the precise mechanisms of DNA synthesis inhibition and mutagenesis remain unclear.

Purpose of the Study:

• To investigate the real-time interactions between DNA polymerases and carcinogenic DNA adducts.
• To elucidate how these adducts affect DNA synthesis and polymerase function.
• To understand the role of adducts in mutagenesis and DNA repair.

Main Methods:

• Employed single-molecule fluorescence techniques to monitor DNA polymerase interactions with DNA containing carcinogenic adducts.
• Analyzed real-time binding dynamics, including polymerase dwell time, binding position, and orientation.
• Investigated the influence of adduct location, structure, and nucleotide availability on polymerase behavior.

Main Results:

• The impact of carcinogenic adducts on DNA polymerase binding is highly dependent on the adduct's location relative to the primer terminus, its chemical structure, and the surrounding nucleotide environment.
• Adducts significantly influence polymerase dwell time, binding position, and orientation on the DNA template.
• A novel adduct- and mismatch-induced intermediate state in DNA polymerase activity was directly observed, potentially representing a key step in the polymerase proofreading mechanism.

Conclusions:

• Carcinogenic adducts directly interfere with DNA polymerase function during replication, impacting enzyme kinetics and binding.
• The observed intermediate state suggests a new mechanistic insight into how DNA polymerases recognize and process damaged DNA.
• Understanding these interactions is critical for deciphering mutagenesis mechanisms and developing strategies to prevent chemically induced cancers.