Pol eta is required for DNA replication during nucleotide deprivation by hydroxyurea

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Hydroxyurea (HU) and UV radiation impede DNA replication through distinct mechanisms.
• DNA polymerase eta (Pol eta), a low-fidelity polymerase, plays a role in DNA damage tolerance.

Purpose of the Study:

• To investigate the role of Pol eta in cellular responses to hydroxyurea-induced nucleotide deprivation and UV damage.
• To elucidate the mechanism by which Pol eta influences S-phase progression and apoptosis.

Main Methods:

• Recruitment of Pol eta to replication forks under HU and UV stress.
• Analysis of cell cycle progression, apoptosis, and DNA damage markers (Mre11/Rad50/Nbs1, H2AX) in wild-type and Pol eta-deficient cells.

Main Results:

• Pol eta is recruited to replication forks by both HU and UV light.
• Under nucleotide deprivation, Pol eta facilitates slow S-phase progression but promotes apoptosis, leading to faster cell death in normal cells compared to Pol eta-deficient cells.
• Pol eta-deficient cells exhibit increased replication fork breakage and DNA damage foci upon HU treatment.

Conclusions:

• Pol eta is essential for S-phase progression under nucleotide-deprived conditions but also acts as a proapoptotic factor.
• Hydroxyurea-induced apoptosis occurs at the G1/S boundary, requiring higher nucleotide concentrations for S-phase initiation than for progression.
• Pol eta functions under suboptimal nucleotide conditions when recruited by hydroxyurea.