Yeast base excision repair: interconnections and networks.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Oxidative DNA damage is a constant threat to genome integrity.
• The base excision repair (BER) pathway is the primary mechanism for removing oxidative base damage in Saccharomyces cerevisiae.
• DNA N-glycosylase/AP lyases initiate the BER pathway.

Purpose of the Study:

• To investigate the roles of BER, nucleotide excision repair (NER), lesion bypass, and recombination pathways in repairing oxidative DNA damage.
• To determine the functional overlap and redundancy between these DNA repair pathways.
• To elucidate the in vivo function of AP lyase activity in BER N-glycosylases.

Main Methods:

• Generating yeast strains with multiple gene disruptions in DNA repair pathways (BER, NER, REV3, RAD52).
• Assessing sensitivity to oxidizing agents (cell killing).
• Evaluating spontaneous hyperrecombinogenic and mutator phenotypes.

Main Results:

• Multiple BER gene disruptions did not cause hypersensitivity to oxidizing agents but led to hyper-recombination and mutator phenotypes.
• Eliminating the NER pathway further enhanced the hyper-recombinogenic and mutator phenotypes.
• Disrupting lesion bypass (REV3) or recombination (RAD52) pathways specifically enhanced mutator or hyper-recombinogenic phenotypes, respectively.
• Cell killing by oxidizing agents required simultaneous elimination of multiple repair pathways.

Conclusions:

• BER, NER, recombination, and lesion bypass pathways exhibit overlapping specificities for removing or tolerating oxidative DNA damage in yeast.
• These pathways play redundant roles in maintaining genome stability against oxidative stress.
• AP lyase activity of BER N-glycosylases has a significant physiological role in vivo.