Evidence for hSNM1B/Apollo functioning in the HSP70 mediated DNA damage response

Area of Science:

• Molecular Biology
• Cell Biology
• Cancer Research

Background:

• The hSNM1B/Apollo protein is crucial for DNA damage response and telomere maintenance.
• TRF2, a shelterin component, interacts with hSNM1B and has roles in telomere protection and DNA damage response.
• HSP70 chaperones are known to maintain genome stability and are often dysregulated in cancer.

Purpose of the Study:

• To identify novel binding partners of hSNM1B using Tandem-Affinity-Purification and mass spectrometry.
• To investigate the functional significance of hSNM1B interactions in DNA damage response.
• To explore the potential of hSNM1B as a cancer therapeutic target.

Main Methods:

• Tandem-Affinity-Purification coupled with mass spectrometry to identify hSNM1B interactors.
• Co-immunoprecipitation assays to confirm protein-protein interactions.
• Depletion of HSP72 in human fibroblasts and assessment of nuclear hSNM1B foci.
• Analysis of CHK1 phosphorylation at serine 317 in response to UVC irradiation after hSNM1B depletion.

Main Results:

• HSC70, HSP72, HSP60, and beta-Tubulin were identified as novel hSNM1B-interacting proteins.
• hSNM1B directly interacts with HSP70 and binds to the substrate-binding domain of HSP72.
• Depletion of HSP72 reduced nuclear hSNM1B foci, and hSNM1B depletion attenuated CHK1 phosphorylation following UVC irradiation.
• hSNM1B enhances ATM and ATR substrate phosphorylation in response to DNA damage.

Conclusions:

• hSNM1B collaborates with HSP70 chaperones in DNA damage response pathways.
• The role of HSP70 in genome stability may be partly mediated by hSNM1B.
• hSNM1B's function in DNA damage response and its interaction with chaperones suggest it as a potential target for cancer therapy.