TOPORS modulates H2AX discriminating genotoxic stresses

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• Histone H2AX is crucial for DNA repair and apoptosis following DNA damage.
• Understanding the regulation of H2AX is vital for comprehending cellular responses to genotoxic stress.

Purpose of the Study:

• To investigate the interaction between TOPORS and H2AX under various DNA damaging conditions.
• To elucidate the role of TOPORS as an E3 ligase in H2AX ubiquitination and turnover.

Main Methods:

• Mammalian cell extracts were exposed to DNA damaging agents (ionizing radiation, doxorubicin, camptothecin, hydrogen peroxide).
• In vitro ubiquitination assays were performed to assess TOPORS' ligase activity.
• Protein-protein interactions and stability were analyzed under different stress conditions.

Main Results:

• TOPORS was confirmed to interact with H2AX and function as an E3 ligase for H2AX ubiquitination.
• TOPORS dissociated from H2AX under oxidative stress but not replication stress.
• Ectopic expression of TOPORS decreased H2AX stability, while oxidative stress recovered H2AX levels.

Conclusions:

• TOPORS plays a significant role in the turnover of H2AX protein.
• TOPORS's function in H2AX regulation is selective, differentiating between oxidative and replication-induced DNA damage.