DNA replication initiation factor RECQ4 possesses a role in antagonizing DNA replication initiation.

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• The conserved C-terminus of Rothmund-Thomson syndrome helicase RECQ4 is crucial for preventing tumorigenesis, but its function is poorly understood.
• While the RECQ4 N-terminus is implicated in DNA replication initiation, the C-terminus's role remains elusive.

Purpose of the Study:

• To elucidate the function of the RECQ4 C-terminus in DNA replication and its relation to cancer.
• To investigate the interaction of RECQ4 with the anaphase-promoting complex/cyclosome (APC/C) and its impact on cell cycle regulation.

Main Methods:

• Unbiased proteomic analysis to identify protein interactions.
• Chromatin immunoprecipitation assays to confirm protein binding.
• Cell-based assays to assess DNA replication, cell cycle progression, and protein stability.

Main Results:

• Identified an interaction between the RECQ4 N-terminus and the APC/C on human chromatin.
• Demonstrated that this interaction stabilizes CDH1, enhancing APC/C-mediated Geminin degradation and promoting replication factor accumulation.
• Showed that the RECQ4 C-terminus inhibits this process by binding to APC/C inhibitors.
• Observed that C-terminal deletion mutations in RECQ4 accelerate replication initiation and G1/S transition, leading to increased DNA content.

Conclusions:

• The RECQ4 C-terminus acts as a negative regulator of DNA replication initiation by antagonizing the N-terminus.
• This regulatory function is essential for preventing uncontrolled cell proliferation and tumorigenesis.
• Oncogenic mutations affecting the RECQ4 C-terminus disrupt this suppression, contributing to cancer development.