RESUMO
FAAP20 is a Fanconi anemia (FA) protein that associates with the FA core complex to promote FANCD2/FANCI monoubiquitination and activate the damage response to interstrand crosslink damage. Here, we report that FAAP20 has a marked role in homologous recombination at a DNA double-strand break not associated with an ICL and separable from its binding partner FANCA. While FAAP20's role in homologous recombination is not dependent on FANCA, we found that FAAP20 stimulates FANCA's biochemical activity in vitro and participates in the single-strand annealing pathway of double-strand break repair in a FANCA-dependent manner. This indicates that FAAP20 has roles in several homology-directed repair pathways. Like other homology-directed repair factors, FAAP20 loss causes a reduction in nuclear RAD51 Irradiation-induced foci; and sensitizes cancer cells to ionizing radiation and PARP inhibition. In summary, FAAP20 participates in DNA double strand break repair by supporting homologous recombination in a non-redundant manner to FANCA, and single-strand annealing repair via FANCA-mediated strand annealing activity.
Assuntos
Anemia de Fanconi , Humanos , Anemia de Fanconi/genética , Reparo de DNA por Recombinação , Quebras de DNA de Cadeia Dupla , Reparo do DNA , Recombinação Homóloga , Proteínas de Grupos de Complementação da Anemia de Fanconi/genéticaRESUMO
Fanconi anemia (FA) is a recessive genetic disorder caused by biallelic mutations in at least one of 22 FA genes. Beyond its pathological presentation of bone marrow failure and congenital abnormalities, FA is associated with chromosomal abnormality and genomic instability, and thus represents a genetic vulnerability for cancer predisposition. The cancer relevance of the FA pathway is further established with the pervasive occurrence of FA gene alterations in somatic cancers and observations of FA pathway activation-associated chemotherapy resistance. In this article we describe the role of the FA pathway in canonical interstrand crosslink (ICL) repair and possible contributions of FA gene alterations to cancer development. We also discuss the perspectives and potential of targeting the FA pathway for cancer intervention.
RESUMO
RAD52 rejoins resected broken DNA ends by mediating single-strand annealing. Our recent work elucidates that FANCA, a Fanconi anemia protein, also directly repairs double-strand breaks (DSBs) by catalyzing annealing of single-stranded DNA. FANCA and RAD52 likely play complementary roles to each other to prevent deleterious consequences of DSBs. Abbreviations: DSBs: DNA double-strand breaks; ICL: interstrand crosslink; ssDNA: single-stranded DNA; HR: homologous recombination; SSA: single-strand annealing; MMEJ: microhomology-mediated end joining; NHEJ: non-homologous end joining; GFP: green fluorescence protein.
RESUMO
FANCA is a component of the Fanconi anemia (FA) core complex that activates DNA interstrand crosslink repair by monoubiquitination of FANCD2. Here, we report that purified FANCA protein catalyzes bidirectional single-strand annealing (SA) and strand exchange (SE) at a level comparable to RAD52, while a disease-causing FANCA mutant, F1263Δ, is defective in both activities. FANCG, which directly interacts with FANCA, dramatically stimulates its SA and SE activities. Alternatively, FANCB, which does not directly interact with FANCA, does not stimulate this activity. Importantly, five other patient-derived FANCA mutants also exhibit deficient SA and SE, suggesting that the biochemical activities of FANCA are relevant to the etiology of FA. A cell-based DNA double-strand break (DSB) repair assay demonstrates that FANCA plays a direct role in the single-strand annealing sub-pathway (SSA) of DSB repair by catalyzing SA, and this role is independent of the canonical FA pathway and RAD52.
Assuntos
Reparo do DNA por Junção de Extremidades , Reparo de Erro de Pareamento de DNA , DNA/genética , Proteína do Grupo de Complementação A da Anemia de Fanconi/genética , Proteína do Grupo de Complementação G da Anemia de Fanconi/genética , Proteínas de Grupos de Complementação da Anemia de Fanconi/genética , Reparo de DNA por Recombinação , Animais , Baculoviridae/genética , Baculoviridae/metabolismo , Linhagem Celular Tumoral , Clonagem Molecular , DNA/metabolismo , Quebras de DNA de Cadeia Dupla , Células Epiteliais/citologia , Células Epiteliais/metabolismo , Proteína do Grupo de Complementação A da Anemia de Fanconi/metabolismo , Proteína do Grupo de Complementação G da Anemia de Fanconi/metabolismo , Proteínas de Grupos de Complementação da Anemia de Fanconi/metabolismo , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Humanos , Mariposas , Osteoblastos/citologia , Osteoblastos/metabolismo , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismoRESUMO
Persistent dysregulation of the DNA damage response and repair in cells causes genomic instability. The resulting genetic changes permit alterations in growth and proliferation observed in virtually all cancers. However, an unstable genome can serve as a double-edged sword by providing survival advantages in the ability to evade checkpoint signaling, but also creating vulnerabilities through dependency on alternative genomic maintenance factors. The Fanconi anemia pathway comprises an intricate network of DNA damage signaling and repair that are critical for protection against genomic instability. The importance of this pathway is underlined by the severity of the cancer predisposing syndrome Fanconi anemia which can be caused by biallelic mutations in any one of the 21 genes known thus far. This review delineates the roles of the Fanconi anemia pathway and the molecular actions of Fanconi anemia proteins in confronting replicative, oxidative, and mitotic stress.