Akt/PKB suppresses DNA damage processing and checkpoint activation in late G2

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• Cell cycle checkpoints are crucial for preventing genomic instability.
• DNA damage response pathways regulate cell cycle progression.
• The role of Akt/PKB in DNA damage response is not fully understood.

Purpose of the Study:

• To investigate the DNA damage response in late G2 phase cells.
• To identify factors regulating checkpoint activation and DNA repair in late G2.
• To explore the role of Akt/PKB in this process.

Main Methods:

• Chemical genetics to inhibit Cyclin-dependent kinase 1 (Cdk1).
• Irradiation to induce DNA damage.
• Analysis of DNA damage markers (gamma-H2AX foci).
• Assessment of checkpoint protein recruitment (RPA, ATR, Rad51, CtIP) and activation (Chk1).
• Inhibition of Akt/PKB (protein kinase B).

Main Results:

• Cells arrested in late G2 with Cdk1 inhibition cannot delay mitotic entry after irradiation.
• Late G2 cells detect DNA damage but fail to activate Chk1 due to impaired DNA double-strand break processing.
• Essential DNA repair proteins (RPA, ATR, Rad51, CtIP) are not recruited to damage sites.
• Inhibition of Akt/PKB restores DNA damage processing and Chk1 activation in late G2 cells.

Conclusions:

• Akt/PKB plays a critical role in regulating DNA repair and checkpoint activation in late G2 phase.
• Impaired DNA damage processing in late G2 cells is linked to Akt activity.
• These findings have implications for cancer therapy, particularly in tumors with activated Akt/PKB.