Contribution of ATM and ATR kinase pathways to p53-mediated response in etoposide and methyl methanesulfonate induced...

Area of Science:

• Molecular Biology
• Genetics
• Toxicology

Background:

• The tumor suppressor p53 is a central regulator of cellular responses to DNA damage.
• DNA damage-sensing kinases modulate p53 activity through post-translational modifications.
• Understanding the specificity of p53 pathway activation is crucial for assessing chemical genotoxicity.

Purpose of the Study:

• To investigate the chemical specificity of the p53 pathway response to DNA damage.
• To determine the role of upstream kinases, particularly ATM, in mediating p53 activation by etoposide (ETP) and methyl methanesulfonate (MMS).

Main Methods:

• Utilized p53-deficient cells and manipulated upstream kinases to assess DNA damage and cellular responses.
• Exposed cells to prototype genotoxic chemicals: etoposide (ETP) and methyl methanesulfonate (MMS).
• Analyzed p53 target protein accumulation, apoptosis, cell cycle arrest, DNA damage markers (p-H2AX, micronuclei), and kinase activation patterns (ATM, ATR, Chk1, Chk2, p38, ERK1/2).

Main Results:

• p53 deficiency reduced apoptosis and increased DNA damage (p-H2AX, micronuclei) in response to both ETP and MMS.
• p53 was not essential for cell cycle arrest in the tested cell lines.
• Inhibition of ATM significantly impacted p53 activation, apoptosis, and DNA damage accumulation more than ATR-Chk1 or MAP kinases, irrespective of the chemical used.
• ETP and MMS induced distinct patterns of downstream kinase activation.

Conclusions:

• ATM is the predominant upstream kinase activating the p53-mediated DNA damage response for both ETP and MMS.
• While ATM activation is conserved, the downstream kinase signaling pathways exhibit chemical-specific differences.