Increased replication-associated single-stranded DNA promotes formaldehyde-induced mutagenesis in Saccharomyces...

Area of Science:

• Molecular Biology
• Genetics
• Toxicology

Background:

• Formaldehyde (FA) is a ubiquitous environmental toxin endogenously produced, known to cause DNA damage, mutations, and cancer.
• FA exposure is associated with specific guanine mutations, forming a mutation signature similar to SBS40.
• Understanding the mechanisms of FA-induced mutagenesis is crucial for assessing its health risks.

Purpose of the Study:

• To investigate the role of replication stress and single-stranded DNA (ssDNA) in formaldehyde-induced mutagenesis.
• To elucidate the specific DNA repair and tolerance pathways involved in preventing FA mutagenesis.

Main Methods:

• Utilized Saccharomyces cerevisiae (yeast) as a model organism.
• Downregulated major replicative polymerases to induce replication defects and ssDNA accumulation.
• Assessed FA sensitivity and mutagenesis in various mutant strains, including those deficient in DNA repair pathways like Mrc1 (CLASPIN) and DNA-protein crosslink repair.
• Investigated the roles of Pol ζ-mediated translesion synthesis and template switching pathways in FA mutagenesis.

Main Results:

• Replication defects leading to ssDNA accumulation significantly increase FA mutagenesis.
• Loss of Mrc1 (CLASPIN) results in high ssDNA and elevated FA mutagenesis, independent of its checkpoint function.
• Defects in DNA-protein crosslink repair confer FA sensitivity but do not alter mutagenesis.
• FA-induced mutagenesis is dependent on Pol ζ translesion synthesis, while template switching is not essential for error-free bypass.

Conclusions:

• Replication-associated ssDNA is a primary target for formaldehyde-induced DNA damage and mutagenesis.
• Specific pathways, including Pol ζ-mediated translesion synthesis, are critical for processing FA adducts during replication.
• Understanding these mechanisms highlights cellular strategies to prevent FA mutagenesis at replication forks.