BRCA1 and BRCA2 5′ noncoding region variants identified in breast cancer patients alter promoter activity and protein binding. Issue 12 (24th September 2018) - Burke, Leslie J.
Abstract: The widespread use of next generation sequencing for clinical testing is detecting an escalating number of variants in noncoding regions of the genome. The clinical significance of the majority of these variants is currently unknown, which presents a significant clinical challenge. We have screened over 6, 000 early‐onset and/or familial breast cancer (BC) cases collected by the ENIGMA consortium for sequence variants in the 5′ noncoding regions of BC susceptibility genes BRCA1 and BRCA2, and identified 141 rare variants with global minor allele frequency < 0.01, 76 of which have not been reported previously. Bioinformatic analysis identified a set of 21 variants most likely to impact transcriptional regulation, and luciferase reporter assays detected altered promoter activity for four of these variants. Electrophoretic mobility shift assays demonstrated that three of these altered the binding of proteins to the respective BRCA1 or BRCA2 promoter regions, including NFYA binding to BRCA1 :c.‐287C>T and PAX5 binding to BRCA2 :c.‐296C>T. Clinical classification of variants affecting promoter activity, using existing prediction models, found no evidence to suggest that these variants confer a high risk of disease. Further studies are required to determine if such variation may be associated with a moderate or low risk of BC. Abstract : We have identified rare single nucleotide variants and small indels mapping to the 5' non‐coding regions of BRCA1 and BRCA2 through targeted sequencing of over 6000 early onset/familial breast cancer patients. We describe four variants in minimal promoter regions that alter gene activity and identify specific transcription factor disruptions for two of these variants. In parallel, we have assessed whether these variants exhibit features expected for high‐risk pathogenic BRCA1 or BRCA2 variants, using available clinical and population data.