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Updated: May 26, 2025
Author Spotlight: Combining Proximity Ligand Assay with Gamma-H2AX Staining to Characterize Protein Interactions in DNA Damage Response
Published on: August 2, 2024
Phosphorylated BLM peptide acts as an agonist for DNA damage response
Ritu Agrawal1,2, Himanshi Agarwal1, Chetana Mukherjee1
1Biotechnology Research and Innovation Council-National Institute of Immunology (BRIC-NII), Aruna Asaf Ali Marg, New Delhi110067, India.
Abstract:
Upon exposure to ionizing irradiation, the MRE11-RAD50-NBS1 complex potentiates the recruitment of ATM (ataxia-telangiectasia mutated) kinase to the double-strand breaks. We show that the lack of BLM causes a decrease in the autophosphorylation of ATM in mice mammary glands, which have lost one or both copies of BLM. In isogenic human cells, the DNA damage response (DDR) pathway was dampened in the absence of BLM, which negatively affected the recruitment of DDR factors onto the chromatin, thereby indicating a direct role of BLM in augmenting DDR. Mechanistically, this was due to the BLM-dependent dissociation of inactive ATM dimers into active monomers. Fragmentation analysis of BLM followed by kinase assays revealed a 20-mer BLM peptide (91-110 aa), sufficient to enhance ATM-dependent p53 phosphorylation. ATM-mediated phosphorylation of BLM at Thr99 within BLM (91-110) peptide enhanced ATM kinase activity due to its interaction with NBS1 and causing ATM monomerization. Delivery of phosphomimetic T99E counterpart of BLM (91-110 aa) peptide led to ATM activation followed by restoration of the DDR even in the absence of ionizing irradiation (both in cells and in BLM knockout mice), indicating its role as a DDR agonist, which can be potentially used to prevent the initiation of neoplastic transformation.
Insights
The BLM protein is crucial for DNA damage response by promoting ATM kinase activation. A specific BLM peptide can activate ATM, restoring DNA repair and potentially preventing cancer.
Area of Science:
- DNA damage response
- Cellular signaling
- Cancer biology
Background:
- The MRE11-RAD50-NBS1 complex recruits ATM kinase to double-strand breaks.
- BLM deficiency impairs ATM autophosphorylation and dampens the DNA damage response (DDR).
Purpose of the Study:
- To elucidate the role of BLM in augmenting the DNA damage response (DDR).
- To identify mechanisms by which BLM influences ATM kinase activity.
- To explore the therapeutic potential of BLM-derived peptides in cancer prevention.
Main Methods:
- Analysis of ATM autophosphorylation in BLM-deficient mice mammary glands.
- Assessment of DDR factor recruitment in isogenic human cells lacking BLM.
- BLM peptide fragmentation and kinase assays.
- Investigation of ATM-mediated phosphorylation of BLM at Thr99.
Main Results:
- BLM deficiency leads to decreased ATM autophosphorylation and impaired DDR.
- BLM promotes ATM activation by dissociating inactive ATM dimers into active monomers.
- A 20-mer BLM peptide (91-110 aa) enhances ATM-dependent p53 phosphorylation.
- ATM-mediated phosphorylation of BLM at Thr99 is critical for ATM activation and DDR restoration.
Conclusions:
- BLM plays a direct role in augmenting the DNA damage response (DDR) by facilitating ATM kinase activation.
- A specific phosphomimetic BLM peptide (T99E) acts as a DDR agonist, activating ATM and restoring DNA repair independently of irradiation.
- This peptide holds potential for preventing neoplastic transformation.
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