p53 Maintains Genomic Stability by Preventing Interference between Transcription and Replication.

Area of Science:

• Molecular Biology
• Genetics
• Cancer Research

Background:

• The p53 tumor suppressor is crucial for maintaining genomic stability through cell-cycle arrest, senescence, and apoptosis.
• Canonical p53 functions do not fully explain its role in preventing DNA damage during replication.
• Replication-transcription conflicts can lead to genomic instability and are implicated in cancer development.

Purpose of the Study:

• To investigate a novel, non-canonical function of p53 in preventing conflicts between DNA transcription and replication.
• To understand the role of p53 in regulating DNA topology and Topoisomerase II activity during S phase.
• To explore therapeutic strategies targeting p53-deficient cells by modulating transcription or Topoisomerase II activity.

Main Methods:

• Utilized isogenic p53 mutant and knockout cell lines.
• Assessed DNA damage and Topoisomerase IIα (TOP2A)-DNA complex formation.
• Employed pharmacologic inhibition of transcription and Topoisomerase II inhibitors.

Main Results:

• p53 deficiency leads to spontaneous DNA damage during replication and increased TOP2A-DNA complex accumulation.
• Replication fork progression is impaired in p53-deficient cells, but this is reversed by transcription inhibition.
• Inhibition of transcription attenuates DNA damage and restores cell viability in p53-deficient cells.

Conclusions:

• p53 plays a critical role in preventing DNA topological stress arising from transcription during S phase, thereby ensuring normal replication fork progression.
• This newly identified function of p53 is independent of its canonical roles in cell-cycle arrest, senescence, and apoptosis.
• Targeting transcription in p53-deficient cancers represents a potential therapeutic strategy to mitigate replication stress and DNA damage.