The ubiquitin ligase APC/C(Cdh1) puts the brakes on DNA-end resection

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• DNA double-strand breaks (DSBs) are critical DNA lesions.
• Their incorrect repair can lead to genomic instability and cancer.
• DNA-end resection is essential for accurate DSB repair and is cell cycle-regulated.

Purpose of the Study:

• To investigate the regulation of DNA-end resection factors during DSB repair.
• To identify novel mechanisms controlling the cell cycle-dependent repair of DSBs.
• To understand the role of the APC/C(Cdh1) complex in DSB repair pathway choice.

Main Methods:

• Utilized cell-based assays to monitor DNA-end resection.
• Employed ubiquitin-proteasome system inhibitors to study protein degradation.
• Investigated the interaction between APC/C(Cdh1) and CtIP using co-immunoprecipitation.
• Performed gene silencing experiments (siRNA) to assess the function of APC/C(Cdh1) and CtIP.

Main Results:

• Identified CtBP-interacting protein (CtIP) as a substrate for APC/C(Cdh1)-mediated degradation.
• Demonstrated that APC/C(Cdh1) activity is required for timely CtIP degradation.
• Showed that CtIP degradation by APC/C(Cdh1) is crucial for efficient DNA double-strand break repair.
• Uncovered a new regulatory layer controlling DNA-end resection dynamics.

Conclusions:

• The APC/C(Cdh1) ubiquitin ligase plays a key role in regulating DSB repair.
• APC/C(Cdh1) ensures the timely degradation of the resection factor CtIP.
• This regulation by APC/C(Cdh1) is vital for preventing genomic instability and is a critical aspect of DSB repair in human cells.