EXO5-DNA structure and BLM interactions direct DNA resection critical for ATR-dependent replication restart

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Replication fork restart is essential for cell survival and genome stability following DNA damage.
• ATR kinase, BLM helicase, and structure-specific nucleases are known regulators of this process.

Purpose of the Study:

• To identify novel factors involved in replication fork restart.
• To elucidate the role of human exonuclease V (EXO5) in this process and its connection to ATR and BLM.

Main Methods:

• Structural, mechanistic, and mutational analyses of EXO5.
• Mass spectrometric analysis to identify protein interactions.
• Cellular assays measuring fork progression, DNA repair, and cell survival.
• Analysis of EXO5 expression in tumor data.

Main Results:

• EXO5 identified as an ATR-regulated, DNA structure-specific nuclease and BLM partner.
• Elevated EXO5 in tumors correlates with increased mutation loads and poorer patient survival.
• EXO5 phosphorylation regulates its nuclease activity and BLM binding.
• EXO5 depletion impairs fork progression, DNA repair, and cell survival, but rescues FANCA-deficient cells.

Conclusions:

• EXO5 plays a critical role in replication fork restart, linking ATR and BLM.
• EXO5 upregulation has oncogenic potential and may serve as a prognostic marker.
• Targeting EXO5 could be a therapeutic strategy for cancers with high mutation loads.