Mechanism of BRCA1-BARD1 function in DNA end resection and DNA protection

DNA double-strand break (DSB) repair by homologous recombination (HR) is initiated by DNA end resection, a process involving the controlled degradation of the 5'-terminated strands at DSB sites. The breast cancer suppressor BRCA1-BARD1 not only promotes resection and HR, but it also protects DNA upon replication stress. BRCA1-BARD1 counteracts the anti-resection and pro-non-homologous end-joining factor 53BP1, but whether it functions in resection directly has been unclear. Using purified recombinant proteins, we show here that BRCA1-BARD1 directly promotes long-range DNA end resection pathways catalyzed by the EXO1 or DNA2 nucleases. In the DNA2-dependent pathway, BRCA1-BARD1 stimulates DNA unwinding by the WRN/BLM helicase. Together with MRE11-RAD50-NBS1 (MRN) and phosphorylated CtIP, BRCA1-BARD1 forms the BRCA1-C complex, which stimulates resection synergistically to an even greater extent. A mutation in phosphorylated CtIP (S327A), which disrupts its binding to the BRCT repeats of B..., In the uploaded files, we present mass photomether and single-molecule magnetic tweezer data from the main and extended data figures. The uploaded files include all the information required to plot the graphs as indicated in the attached main and extended data figures. 
Mass photometry measurements were performed on a TwoMP mass photometer (Refeyn Ltd). First, borosilicate microscope glass plate (No. 1.5 H thickness, 24 x 50 mm, VWR) were cleaned by sequential soaking in Milli-Q-water, isopropanol and Milli-Q-water followed by drying under a stream of clean nitrogen. Next, silicone gaskets (CultureWell Reusable Gasket, Grace Bio-Labs) were placed on the clean coverslip to create a defined well for sample delivery. To convert optical reflection-interference contrast into a molecular mass, a known protein size marker (NativeMark Unstained Protein Standard, Invitrogen) was measured on the same day. For mass measurements, gaskets were filled with 18 ml measurement buffer (25 mM Tris-HCl pH ..., , # Mechanism of BRCA1-BARD1 function in DNA end resection and DNA protection

Here, we present mass photometer data (.mp and .mp4 files) and single-molecule magnetic tweezer data (.dat files) from the main and extended data figures of the manuscript, \" Mechanism of BRCA1-BARD1 function in DNA end resection and DNA protection\". The files uploaded include all the information needed to plot the panels as indicated in the attached main and extended data figures and the file names. 

## Description of the data and file structure

We share information obtained through mass photometry and single-molecule magnetic tweezers techniques presented in the study's main and supplementary figures. 

**Mass photometer data**

We shared the movies where molecules from the indicated sample are visualized based on their optical reflection-interference contrast as black objects with white edges. Each movie was recorded for one minute and analyzed with DiscoverMP to obtain the counts plotted in the images. 

...