CtIP links DNA double-strand break sensing to resection

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• DNA double-strand breaks (DSBs) trigger cellular responses involving ATM kinase activation.
• DSB resection generates single-stranded DNA (ssDNA) essential for DNA damage checkpoint activation and homologous recombination (HR) repair.
• The precise mechanism linking DSB sensing to resection remains incompletely understood.

Purpose of the Study:

• To elucidate the biochemical mechanism governing the transition from DNA double-strand break (DSB) sensing to DNA resection.
• To investigate the role of the tumor suppressor protein CtIP in this critical DNA repair pathway.

Main Methods:

• Experiments were conducted using Xenopus egg extracts and human cell lines.
• Investigated the translocation of CtIP to DSBs.
• Assessed the dependence of CtIP translocation on the Mre11-Rad50-NBS1 complex, ATM kinase activity, and CtIP's DNA-binding motif.

Main Results:

• CtIP translocates to sites of DNA double-strand breaks (DSBs).
• CtIP translocation is dependent on the Mre11-Rad50-NBS1 sensor complex and ATM kinase activity.
• A direct DNA-binding motif in CtIP is essential for its translocation and subsequent promotion of DSB resection.

Conclusions:

• CtIP acts as a critical mediator bridging DSB sensing and DNA resection.
• CtIP facilitates the transition by binding to DSBs post-sensing and ATM activation, thereby promoting resection.
• This action of CtIP is vital for efficient DNA damage checkpoint activation and homologous recombination (HR) repair.