title: Suppression of the DNA repair defects of BRCA2-deficient cells with heterologous protein fusions.
abstract: The BRCA2 tumor suppressor plays an important role in the repair of DNA damage by homologous recombination, also termed homology-directed repair (HDR). Human BRCA2 is 3,418 aa and is composed of several domains. The central part of the protein contains multiple copies of a motif that binds the Rad51 recombinase (the BRC repeat), and the C terminus contains domains that have structural similarity to domains in the ssDNA-binding protein replication protein A (RPA). To gain insight into the role of BRCA2 in the repair of DNA damage, we fused a single (BRC3, BRC4) or multiple BRC motifs to the large RPA subunit. Expression of any of these protein fusions in Brca2 mutant cells substantially improved HDR while suppressing mutagenic repair. A fusion containing a Rad52 ssDNA-binding domain also was active in HDR. Mutations that reduced ssDNA or Rad51 binding impaired the ability of the fusion proteins to function in HDR. The high level of spontaneous chromosomal aberrations in Brca2 mutant cells was largely suppressed by the BRC-RPA fusion proteins, supporting the notion that the primary role of BRCA2 in maintaining genomic integrity is in HDR, specifically to deliver Rad51 to ssDNA. The fusion proteins also restored Rad51 focus formation and cellular survival in response to DNA damaging agents. Because as little as 2% of BRCA2 fused to RPA is sufficient to suppress cellular defects found in Brca2-mutant mammalian cells, these results provide insight into the recently discovered diversity of BRCA2 domain structures in different organisms.
authors.affiliation: Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Saeki
authors.forename: Nicolas
authors.initials: N
authors.lastname: Siaud
authors.forename: Nicole
authors.initials: N
authors.lastname: Christ
authors.forename: Wouter W
authors.initials: WW
authors.lastname: Wiegant
authors.forename: Paul P W
authors.initials: PP
authors.lastname: van Buul
authors.forename: Mingguang
authors.initials: M
authors.lastname: Han
authors.forename: Malgorzata Z
authors.initials: MZ
authors.lastname: Zdzienicka
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Stark
authors.forename: Maria
authors.initials: M
authors.lastname: Jasin
mesh_terms: D000818:Animals; D024682:BRCA2 Protein / Q000737:chemistry / Q000172:deficiency* / Q000378:metabolism*; D002869:Chromosome Aberrations; D006224:Cricetinae; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D051379:Mice; D010641:Phenotype; D011485:Protein Binding; D051135:Rad51 Recombinase / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D011995:Recombination, Genetic; D051716:Replication Protein A / Q000378:metabolism
chemical_list: D024682:BRCA2 Protein; D004277:DNA, Single-Stranded; D011993:Recombinant Fusion Proteins; D051716:Replication Protein A; D051135:Rad51 Recombinase