title: Multimodal assessment of protein functional deficiency supports pathogenicity of BRCA1 p.V1688del.
abstract: Unequivocal discrimination between neutral variants and deleterious mutations is crucial for appropriate counseling of individuals with a BRCA1 or BRCA2 sequence change. An increasing number of variants of uncertain significance (VUS) are being identified, the unclassified biological effect of which poses clinical concerns. A multifactorial likelihood-based approach recently suggested disease causality for BRCA1 p.V1688del, a VUS recurrent in Italian breast/ovarian cancer families. Whether and how this single amino acid deletion in the BRCA1 COOH terminus (BRCT) domain affects the function of the mutant protein (DeltaValBRCA1) has not been elucidated. We undertook comprehensive functional characterization of DeltaValBRCA1, comprising comparative structural modeling, analysis of protein stability and associations, and analysis of DNA repair function. Our model predicted BRCT domain destabilization and folding disruption caused by BRCA1 p.V1688del. Consistently, the recombinant DeltaValBRCA1 was less stable than wild-type BRCA1 and, unlike the latter, failed to associate with BRIP1, CtIP, and Rap80 and to relocalize to sites of DNA damage. Yeast two-hybrid analysis revealed a compromised interaction with FHL2 and KPNA2, which is likely responsible for improper subcellular localization of DeltaValBRCA1. In addition, we found four new breast/ovarian cancer families of Italian ancestry who carried this sequence alteration. These results provide the first evidence of the effect of BRCA1 p.V1688del on protein stability and function, supporting the view that it is a deleterious mutation. Multimodal analyses like ours could advance understanding of tumor suppression by BRCA1 and ultimately contribute to developing efficient strategies for screening and characterization of VUS.
authors.affiliation: Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA. Arcangela_Denicolo@dfci.harvard.edu
authors.forename: Arcangela
authors.initials: A
authors.lastname: De Nicolo
authors.forename: Emilio
authors.initials: E
authors.lastname: Parisini
authors.forename: Quan
authors.initials: Q
authors.lastname: Zhong
authors.forename: Maurizia
authors.initials: M
authors.lastname: Dalla Palma
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Stoeckert
authors.forename: Susan M
authors.initials: SM
authors.lastname: Domchek
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Nathanson
authors.forename: Maria A
authors.initials: MA
authors.lastname: Caligo
authors.forename: Marc
authors.initials: M
authors.lastname: Vidal
authors.forename: Michael E
authors.initials: ME
authors.lastname: Cusick
authors.forename: Judy E
authors.initials: JE
authors.lastname: Garber
mesh_terms: D019943:Amino Acid Substitution; D019313:BRCA1 Protein / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D024682:BRCA2 Protein / Q000737:chemistry / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D005260:Female; D020022:Genetic Predisposition to Disease; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D060850:LIM-Homeodomain Proteins; D008958:Models, Molecular; D009124:Muscle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011485:Protein Binding; D017510:Protein Folding; D055550:Protein Stability; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D019313:BRCA1 Protein; D024682:BRCA2 Protein; C105987:FHL2 protein, human; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D009124:Muscle Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors
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