Pol μ dGTP mismatch insertion opposite T coupled with ligation reveals promutagenic DNA repair intermediate

Area of Science:

• Molecular Biology
• Genetics
• Cancer Research

Background:

• Mismatched nucleotide incorporation during DNA replication and repair is a primary cause of mutations in cancer.
• The dG:dT base pair, resembling Watson-Crick pairing, contributes significantly to genome instability.
• Understanding these mechanisms is crucial for cancer mutation research.

Purpose of the Study:

• To investigate the role of DNA polymerase mu in incorporating mismatched nucleotides.
• To explore the implications of dGTP insertion opposite a template T in DNA repair.
• To determine the potential contribution of these events to mutagenesis in nonhomologous end joining.

Main Methods:

• Utilized a model double-strand break DNA repair substrate.
• Assessed the insertion activity of DNA polymerase mu with 7,8-dihydro-8'-oxo-dGTP (8-oxodGTP) and deoxyguanosine triphosphate (dGTP) opposite a template base T.
• Evaluated the ligation efficiency of the incorporated nucleotides by DNA ligase.

Main Results:

• DNA polymerase mu efficiently inserted both 8-oxodGTP and dGTP opposite a template base T.
• The incorporated dGTP opposite template T was efficiently ligated by DNA ligase.
• This suggests a pathway for generating mutations during DNA repair.

Conclusions:

• DNA polymerase mu-mediated insertion of dGTP opposite template T, followed by ligation, can occur.
• This mechanism may represent a significant source of mutations in nonhomologous end joining.
• These findings shed light on genome instability and mutagenesis in cancer cells.