Novel mutations in the RING-finger domain of BRCA1 gene in clinically diagnosed breast cancer patients.

In the present study, we investigated the frequency of BRCA1 gene mutations in 30 breast cancer (BC) patients of independent family history and 30 healthy control subjects. The immunohistochemistry (IHC) of BC patients showed duct cell carcinoma and distinct expression of the human epidermal growth factor receptor 2 (HER2). The genomic DNA was extracted from the BC patients and control subjects, the BRCA1 gene was PCR amplified and sequenced. The sequence analysis revealed that BRCA1 gene mutations were detected in 5/30 (16.6%) unrelated patients. One novel deleterious c.53delT mutation was detected in 3/30 (10%) unrelated patients leading to p.Met18Serfs*5 frame shift mutation in exon 2. Two patients 2/30 (6%) had novel c.297_301delinsCTCAA mutation in exon 5 leading to p.Leu99_Tyr101delinsPheSerAsn. Interestingly, the qRT-PCR analysis showed high expression of BRCA1 gene in all these patients having mutations compared with control subjects. Further, in silico analysis revealed loss of zinc-binding region of the RING-finger domain in BRCA1 structure due to these mutations, variable number of helices, helix-helix interactions, β-turns, and γ-turns were identified in the secondary structure, resulted in the formation of non-functional protein which is unable to activate BRCA1-associated genome surveillance complex (BASC) leading to uncontrolled cell proliferation. Moreover, the molecular dynamics (MD) simulations of mutated BRCA1 protein demonstrated extensive variations in the domain and non-domain regions compared with the wild-type structure as indicated by RMSD values. All these results conclusively explain that the c.53delT mutation may be the probable founder of deleterious mutation in this ethnic group. © King Abdulaziz City for Science and Technology 2020.