DNA repair factor RAD18 and DNA polymerase Polκ confer tolerance of oncogenic DNA replication stress

Area of Science:

• Molecular Biology
• Cancer Biology
• DNA Repair

Background:

• Neoplastic cells develop mechanisms to cope with oncogene-induced DNA replication stress.
• Cyclin-dependent kinase 2 (CDK2) is a key mediator of this oncogenic stress.

Purpose of the Study:

• To elucidate the mechanisms by which cancer cells tolerate CDK2-mediated DNA replication stress.
• To identify key proteins involved in this tolerance pathway.

Main Methods:

• Investigated the activation of DNA repair protein RAD18 by CDK2-inducing stimuli (Cyclin E, RAS, WEE1 inhibition).
• Assessed the role of RAD18 and DNA polymerase κ (Polκ) in sustaining DNA synthesis under elevated CDK2 activity.
• Examined the consequences of RAD18 deficiency on DNA replication and cell cycle progression.
• Evaluated the sensitivity of RAD18-deficient cells to WEE1 inhibitor MK-1775.

Main Results:

• CDK2-inducing stimuli activated RAD18, a process dependent on DNA synthesis initiation and repressed by p53.
• RAD18 and Polκ were essential for maintaining DNA synthesis in cells with high CDK2 activity.
• RAD18-deficient cells accumulated single-stranded DNA (ssDNA) and required the G2/M checkpoint to prevent mitotic entry.
• Cells lacking RAD18 or Polκ were highly sensitive to WEE1 inhibition.

Conclusions:

• The RAD18-Polκ signaling axis is critical for tolerating CDK2-mediated oncogenic DNA replication stress.
• This pathway may enable neoplastic cells to overcome barriers to tumorigenesis.
• Targeting this axis could offer therapeutic strategies against cancer.