Human DNA polymerase beta mutations allowing efficient abasic site bypass.

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• DNA damage occurs frequently, with abasic sites being a common lesion.
• Abasic sites impede DNA synthesis and repair by DNA polymerases.
• The precise mechanisms by which DNA polymerases fail to bypass abasic sites are not fully understood.

Purpose of the Study:

• To identify specific amino acid residues in human DNA polymerase β that influence its pausing at abasic sites.
• To investigate the role of DNA polymerase β in DNA replication, repair, and its potential link to cancer.

Main Methods:

• High-throughput screening of over 11,000 variants of human DNA polymerase β.
• Characterization of mutant enzyme activity and fidelity on damaged and undamaged DNA.
• Crystallographic analysis of a selected mutant.

Main Results:

• Two mutants, E232K and T233I, demonstrated an enhanced ability to incorporate nucleotides opposite abasic sites.
• These variants also exhibited increased overall activity and reduced fidelity on undamaged DNA.
• Mutations were identified in known functional regions of DNA polymerase β, offering novel insights.

Conclusions:

• The E232K and T233I substitutions in DNA polymerase β facilitate nucleotide incorporation opposite abasic sites.
• These findings provide mechanistic insights into DNA polymerase bypass of lesions and have implications for DNA repair and cancer research.