Functional evaluation of BRCA2 variants mapping to the PALB2-binding and C-terminal DNA-binding domains using a mouse ES cell-based assay.
Single-nucleotide substitutions and small in-frame insertions or deletions identified in human breast cancer susceptibility genes BRCA1 and BRCA2 are frequently classified as variants of unknown clinical significance (VUS) due to the availability of very limited information about their functional consequences. Such variants can most reliably be classified as pathogenic or non-pathogenic based on the data of their co-segregation with breast cancer in affected families and/or their co-occurrence with a pathogenic mutation. Biological assays that examine the effect of variants on protein function can provide important information that can be used in conjunction with available familial data to determine the pathogenicity of VUS. In this report, we have used a previously described mouse embryonic stem (mES) cell-based functional assay to characterize eight BRCA2 VUS that affect highly conserved amino acid residues and map to the N-terminal PALB2-binding or the C-terminal DNA-binding domains. For several of these variants, very limited co-segregation information is available, making it difficult to determine their pathogenicity. Based on their ability to rescue the lethality of Brca2-deficient mES cells and their effect on sensitivity to DNA-damaging agents, homologous recombination and genomic integrity, we have classified these variants as pathogenic or non-pathogenic. In addition, we have used homology-based modeling as a predictive tool to assess the effect of some of these variants on the structural integrity of the C-terminal DNA-binding domain and also generated a knock-in mouse model to analyze the physiological significance of a residue reported to be essential for the interaction of BRCA2 with meiosis-specific recombinase, DMC1.
Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA.
Kajal
K
Biswas
Ranabir
R
Das
Julie M
JM
Eggington
Huanyu
H
Qiao
Susan L
SL
North
Stacey
S
Stauffer
Sandra S
SS
Burkett
Betty K
BK
Martin
Eileen
E
Southon
Scott C
SC
Sizemore
Dmitry
D
Pruss
Karla R
KR
Bowles
Benjamin B
BB
Roa
Neil
N
Hunter
Lino
L
Tessarollo
Richard J
RJ
Wenstrup
R Andrew
RA
Byrd
Shyam K
SK
Sharan
D000595:Amino Acid Sequence; D000818:Animals; D024682:BRCA2 Protein / Q000737:chemistry / Q000235:genetics*; D001943:Breast Neoplasms / Q000235:genetics*; D018797:Cell Cycle Proteins; D002470:Cell Survival; D002478:Cells, Cultured; D002874:Chromosome Mapping; D017124:Conserved Sequence; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004268:DNA-Binding Proteins; D053595:Embryonic Stem Cells / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D000076164:Fanconi Anemia Complementation Group N Protein; D005260:Female; D056726:Genetic Association Studies; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D016685:Mitomycin / Q000494:pharmacology; D008958:Models, Molecular; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D020836:Protein Structure, Quaternary; D040681:Structural Homology, Protein; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D024682:BRCA2 Protein; C551750:BRCA2 protein, human; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D000076164:Fanconi Anemia Complementation Group N Protein; D009153:Mutagens; D009687:Nuclear Proteins; C512790:PALB2 protein, human; D025521:Tumor Suppressor Proteins; D016685:Mitomycin; C074556:DMC1 protein, human