DNA-PK controls Apollo's access to leading-end telomeres.

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Telomere Biology

Background:

• The Ku70/80 and DNA-PKcs (DNA-PK) complex is crucial for DNA double-strand break repair via canonical non-homologous end joining (c-NHEJ).
• DNA-PK also plays a paradoxical role in preventing fusions of newly replicated leading-end telomeres.

Purpose of the Study:

• To elucidate the role of DNA-PK in regulating Apollo/DCLRE1B/SNM1B, the nuclease responsible for resecting leading-end telomeres.
• To investigate the molecular mechanisms underlying DNA-PK's control over Apollo's telomeric function.

Main Methods:

• Biochemical assays to assess DNA-PK's interaction with Apollo.
• AlphaFold-Multimer for structural prediction of the Apollo-DNA-PKcs complex.
• Analysis of DNA-PKcs kinase activity and phosphorylation sites (ABCDE/Thr2609 cluster).

Main Results:

• The telomeric function of Apollo necessitates DNA-PKcs kinase activity and direct binding to DNA-PK.
• Structural predictions indicate extensive interactions between Apollo's nuclease domain and DNA-PKcs.
• DNA-PK's telomeric function is dependent on the ABCDE/Thr2609 phosphorylation cluster, similar to Artemis regulation.

Conclusions:

• DNA-PK regulates leading-end telomere resection by binding to Apollo and facilitating its positioning at the DNA end via phosphorylation.
• This mechanism is analogous to, but distinct from, DNA-PK's regulation of Artemis during V(D)J recombination.
• These findings reveal a novel role for DNA-PK in maintaining telomere integrity.