Understanding the functions of the BRCA protein complexes in DNA break repair and in replication stress

Project Information

BRCA INSIGHTS

Grant agreement ID: 101018257

DOI

10.3030/101018257

EC signature date 3 June 2021

Start date 1 April 2022

End date 31 March 2027

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 868 152,50

EU contribution

€ 1 868 152,50

Coordinated by

FONDAZIONE PER L'ISTITUTO DI RICERCA IN BIOMEDICINA
Switzerland

Periodic Reporting for period 2 - BRCA INSIGHTS (Understanding the functions of the BRCA protein complexes in DNA break repair and in replication stress)

Reporting period: 2023-10-01 to 2025-03-31

Summary of the context and overall objectives of the project

The BRCA INSIGHTS project aims to uncover the molecular mechanisms by which BRCA1 and BRCA2 proteins contribute to DNA double-strand break (DSB) repair and replication fork stability. These tumor suppressor proteins are frequently mutated in familial and sporadic breast and ovarian cancers. While their canonical role in DSB repair through homologous recombination is established, their emerging non-canonical roles in replication fork protection and remodeling under stress remain poorly understood. This project employs advanced biochemical techniques to define the precise functions of BRCA proteins in these processes, leveraging state-of-the-art protein purification and controlled experimental systems.

Understanding how BRCA1 and BRCA2 function to maintain genome stability addresses critical gaps in cancer biology. Insights from this research have the potential to influence cancer treatment by improving the understanding of chemoresistance mechanisms in BRCA-mutated tumors and identifying new therapeutic targets. By advancing basic knowledge, the project ultimately aligns with the goals of reducing cancer burden and improving cancer therapy through precision medicine.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We explored how cells repair DNA damage, particularly DNA double-strand breaks (DSBs). DNA break repair is essential for preventing mutations that can lead to diseases such as cancer. Our research focused on a specific protein complex called BRCA1–BARD1, which is widely known for its role in suppressing breast and ovarian cancers.

We discovered that BRCA1–BARD1 complex plays a crucial role in promoting long-range DNA end resection during homologous recombination. DNA end resection is a critical early step in DSB repair. This process involves the controlled degradation of one strand of DNA at the site of the break to generate a single-stranded DNA (ssDNA) overhang. The ssDNA overhang serves as a platform for the recruitment and binding of proteins required for high-fidelity repair through homologous recombination (HR).

Specifically, the study demonstrates that BRCA1–BARD1 directly stimulates the activities of the nucleases EXO1 and DNA2, along with their associated helicases Werner (WRN) or Bloom (BLM). The BRCA1–BARD1 complex enhances the helicase function, facilitating DNA unwinding required for resection. Additionally, the formation of the BRCA1–C complex, involving phosphorylated CtIP and MRN, further boost the resection process.

Together, our data provided key novel insights the the function of the BRCA1-BRCA2 complex in DNA repair.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The results in our first publication surpass the current state of the art by providing a more detailed mechanistic understanding of the role of the BRCA1–BARD1 complex in DNA end resection, a critical step in DNA double-strand break (DSB) repair. Moving forward, we will focus also on the role of BRCA2, and study how the protein function in DNA break repair and how they support DNA replication.

A cartoon showing the function of the BRCA1-BARD1 complex in DNA end resection