Thymine-thymine dimer bypass by yeast DNA polymerase zeta

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• DNA damage can impede replication, leading to mutations.
• Specific genes like REV3 and REV7 in Saccharomyces cerevisiae are implicated in DNA damage tolerance.
• Understanding the mechanisms of DNA repair and mutagenesis is vital for cellular health.

Purpose of the Study:

• To investigate the role of REV3 and REV7 in DNA damage-induced mutagenesis.
• To characterize the enzymatic activity of the Rev3-Rev7 protein complex.
• To compare the efficiency of DNA lesion bypass by the Rev3-Rev7 complex versus other DNA polymerases.

Main Methods:

• Genetic analysis of REV3 and REV7 genes in yeast.
• Biochemical purification and characterization of the Rev3-Rev7 protein complex.
• In vitro replication assays using DNA templates containing thymine-thymine cis-syn cyclobutane dimers.

Main Results:

• The Rev3-Rev7 proteins form a complex with DNA polymerase activity.
• This complex, identified as DNA polymerase zeta, replicated past thymine-thymine dimers with approximately 10% efficiency.
• Yeast DNA polymerase alpha showed significantly lower bypass efficiency (≤1%) for the same lesion.

Conclusions:

• The Rev3-Rev7 complex, DNA polymerase zeta, plays a key role in bypassing DNA damage-induced lesions.
• DNA polymerase zeta is more efficient at translesion synthesis than DNA polymerase alpha.
• This finding identifies a novel eukaryotic DNA polymerase involved in maintaining genomic integrity after DNA damage.