Replication fork integrity and intra-S phase checkpoint suppress gene amplification.

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Gene amplification, a driver of chromosome instability, originates from DNA double-strand breaks (DSBs).
• Mutant p53 compromises cell cycle checkpoints, facilitating gene amplification.
• The MRN (Mre11/Rad50/Nbs1) complex is vital for DNA double-strand break repair.

Purpose of the Study:

• To investigate the role of the MRN complex in spontaneous gene amplification.
• To determine if MRN complex impairment can induce gene amplification independently of p53 status.
• To elucidate the mechanisms by which MRN complex dysfunction leads to replication stress and DNA damage.

Main Methods:

• Analysis of gene amplification in mammalian cells with impaired MRN complex function.
• Assessment of replication stress markers, including single-stranded DNA breaks.
• Evaluation of ATM/ATR-mediated checkpoint activation and cell cycle progression.
• Global gene expression analysis to identify cellular adaptation strategies.

Main Results:

• Impaired MRN complex function renders mammalian cells proficient for spontaneous gene amplification.
• MRN complex deficiency leads to replication stress and accumulation of replication-associated DSBs, primarily via replication fork reversal.
• Compromised ATM/ATR checkpoints allow cell cycle progression despite DSBs, promoting gene amplification independently of p53.
• Cells adapt to replication stress by downregulating DNA replication and cell cycle progression genes.

Conclusions:

• The MRN complex acts as a critical suppressor of gene amplification.
• MRN complex stabilizes replication forks and ensures proper DNA damage response to replication-associated DSBs.
• MRN complex function is essential for preventing chromosome instability and maintaining genomic integrity.