DNA polymerase ζ is a robust reverse transcriptase

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• DNA double-strand break (DSB) repair can utilize RNA templates, a process distinct from canonical DNA-templated repair.
• This RNA-templated repair necessitates reverse transcriptase activity to synthesize DNA from an RNA template.
• Translesion synthesis (TLS) DNA polymerases (Pol) are candidates for this reverse transcription due to their promiscuity.

Purpose of the Study:

• To investigate and compare the reverse transcriptase activities of all seven known nuclear DNA polymerases in *Saccharomyces cerevisiae*.
• To identify the specific DNA polymerase responsible for RNA-templated DSB repair in yeast.

Main Methods:

• Purification of all seven nuclear DNA polymerases from *Saccharomyces cerevisiae*.
• Comparative analysis of the reverse transcriptase activities of the purified DNA polymerases.
• Assessment of the impact of regulatory factors (RPA, RFC/PCNA) on Pol ζ activity.

Main Results:

• Yeast Pol ζ exhibits significantly higher reverse transcriptase activity compared to Pol η and other DNA polymerases.
• Pol ζ's reverse transcriptase activity is independent of RPA and RFC/PCNA.
• Pol ζ functions distributively to synthesize DNA complementary to an RNA template strand.

Conclusions:

• Pol ζ is the predominant DNA polymerase involved in RNA-templated DSB repair in *Saccharomyces cerevisiae*.
• The findings support the role of Pol ζ in facilitating DNA repair using RNA templates, consistent with in vivo studies.