title: BRCA2-dependent and independent formation of RAD51 nuclear foci.
abstract: The formation of RAD51 foci in response to ionizing radiation (IR) represents an important step in the repair of DNA double-strand breaks. RAD51 foci also appear during S phase and are thought to be required for the restart of stalled or broken replication forks. The RAD51 recombinase interacts directly with the breast cancer-associated tumour suppressor BRCA2, an interaction that is required for normal recombination proficiency, radiation resistance and genome stability. In CAPAN-1 cells, which express a truncated form of BRCA2 that is cytoplasmic because of loss of the nuclear localization signal, the formation of IR-induced RAD51 foci is impaired. In this work, we show that S-phase RAD51 foci form normally in CAPAN-1 cells expressing truncated BRCA2. Moreover, we find that RAD51 specifically associates with chromatin at S phase in a reaction that is BRCA2-independent. The observed BRCA2-dependent and independent formation of RAD51 foci shows that intact BRCA2 is not required for RAD51 focus formation per se, leading us to suggest that S phase and IR-induced RAD51 foci assemble by distinct pathways with defined protein requirements.
authors.affiliation: Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, UK.
authors.forename: Madalena
authors.initials: M
authors.lastname: Tarsounas
authors.forename: Derek
authors.initials: D
authors.lastname: Davies
authors.forename: Stephen C
authors.initials: SC
authors.lastname: West
mesh_terms: D021581:Active Transport, Cell Nucleus; D024682:BRCA2 Protein / Q000172:deficiency / Q000378:metabolism*; D001943:Breast Neoplasms / Q000473:pathology; D002277:Carcinoma / Q000473:pathology; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics / Q000502:physiology*; D004261:DNA Replication / Q000235:genetics / Q000502:physiology*; D004273:DNA, Neoplasm / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000378:metabolism*; D024522:Genes, BRCA2; D006367:HeLa Cells / Q000528:radiation effects; D006801:Humans; D009097:Multienzyme Complexes / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000473:pathology; D021382:Protein Sorting Signals; D051135:Rad51 Recombinase; D016196:S Phase; D014407:Tumor Cells, Cultured / Q000528:radiation effects
chemical_list: D024682:BRCA2 Protein; D002843:Chromatin; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D009097:Multienzyme Complexes; D009363:Neoplasm Proteins; D021382:Protein Sorting Signals; C495153:RAD51 protein, human; D051135:Rad51 Recombinase