Abstract 1282: Analysis of missense variants in BRCA1 BRCT domains

Abstract

Abstract Currently, only ~¼ (133/600) of documented single nucleotide variation leading to missense changes in the BRCA1 gene have been characterized as pathogenic or non-pathogenic (IARC Classes 4 & 5 and 1 & 2, respectively) posing a challenge for carriers of these variants. A detailed understanding of structure-function relationships is critical for the assessment of these variants in the interpretation of data from functional assay and for the development of functional impact predictors. Thus, we have systematically probed the C-terminus of BRCA1 including the N-terminal border of the BRCT domains (M1650, S1651), the BRCT linker region (G1738, D1739, V1740, G1743, H1746, G1748, P1749, R1753, and D1757), and the alpha 1 and alpha’1 helices in BRCT[N] and [C], respectively. We assessed the functional impact of 47 missense variants using a validated transcriptional assay by a protein fusion of the GAL4 DNA-binding domain to BRCA1 C-terminus (aa 1,396-1,863) in HEK 293FT cells. Analysis of functional data redefined the BRCT border (previously thought to be at S1651) at residue M1650. Overall, mutations in the BRCT linker had severe impact on the function. Mutations in the alpha1 and alpha’1 helices also tended to display impaired function despite the lack of functional impact of 16 out of the 17 variants previously analyzed. In summary, our study provides increased granularity in our understanding of BRCA1 regions less tolerant to changes and therefore more likely to contain pathogenic variants. This knowledge will be critical for the assignment of different prior probabilities of pathogenicity given the variant location, improving risk assessment and clinical management of carriers of BRCA1 missense alleles Note: This abstract was not presented at the meeting. Citation Format: Giuliano Di Pietro, Vanessa Camara Fernandes, Kwabena Amankwah, Cara Shields, Volha A. Golubeva, Carly Harro, Marcelo Alex Carvalho, Alvaro N. Monteiro. Analysis of missense variants in BRCA1 BRCT domains [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1282. doi:10.1158/1538-7445.AM2017-1282