Abstract 868: Novel pathogenic mutations in BRCA1 gene that may influence the interaction of BRCA1 protein with BARD1 protein in breast cancer patients

Abstract Breast cancer (BC) contributes to 30% of all women suffering from cancer in the US. Despite enhanced survival rates and recovery rates, pathogenic mutation discovery remains indispensable for early detection and prognosis. BRCA1 pathogenic mutations increase the chance of BC to 55% by the age of 70. A crucial mechanism of mutations is affecting protein-protein interaction. BRCA1 interacts with the BARD1 protein forming a complex that contributes to DNA repair and plays a vital role in tumor suppression. In this study, we aimed to investigate mutations that contribute to the dysfunction of BRCA1 protein through sequencing and computational analysis and their impact on the active site interacting with BRCA1 associated Ring Domain 1 (BRAD1) of BRCA1, and hence its beneficial role in BC prognosis. Herein, we represent a study on 48 BC patients sequenced using Devyser BRCA NGS kit, according to the manufacturer’s instructions. The reagent kit V2, 500 Cycles PE, on the Illumina MiSeq System. Using the Illumina MiSeq System to detect pathogenic mutations. Bioinformatics analysis was carried out for variant calling and different databases, such as ClinVar and BIC, were searched to identify the novel mutations. P2RANK software was used to identify and confirm the active site protein sequences. For BRCA1, we studied three missense mutations present in the ring domain of the protein interacting with BRAD1. We used PDBsum server to retrieve protein structures predicted by the Artificial Intelligence (AI)-based AlphaFold software. Structures were further confirmed using Ramachandran plot. We used Dynamut server to study the stability and structural variability due to mutations. Docking was carried out using HDock software and significant poses were sorted out based on their RMSD values. For BRCA1, Cys47Ser and Cys39Arg caused destabilization of the protein represented as Gibb’s energy by -2.257 kcal/mol and -0.318 kcal/mol respectively. On the other hand, Cys39Tyr caused the stabilization of protein by 0.247 kcal/mol. The effect of mutations on rigidity was determined in terms of vibrational entropy where Cys47Ser caused an increase of protein flexibility with the energy of 0.262 kcal.mol−1.K−1. Cys39Arg and Cys39Tyr decreased the flexibility of the protein and caused rigidity by -0.164 kcal.mol−1.K−1 and -0.371 kcal.mol−1.K−1 respectively. In, conclusion, investigating the three selected pathogenic mutations showed a clear impact on the structure of the protein favored different types of bonds in the active site that may alter the interaction between BRCA1 and BARD1. This study has a beneficial role to investigate the impact of BRCA1 mutations on the structural stability of the protein and thereby the risk of BC development Citation Format: Yahia Ahmad Yahia, Nasra F. Abdel Fattah, Marwa A. Abdel Wahed, Fatma S S Hafez, Sara HA Arwa, Samah A. Loutfy. Novel pathogenic mutations in BRCA1 gene that may influence the interaction of BRCA1 protein with BARD1 protein in breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 868.