title: DNA damage induces p53-dependent BRCA1 nuclear export.
abstract: The tumor suppressor gene BRCA1 plays an important role in the response to DNA damage. BRCA1 function is regulated by a variety of mechanisms including transcriptional control, phosphorylation, and protein-protein interactions. Recent studies have shown that BRCA1 is a nuclear-cytoplasmic shuttle protein. Its subcellular localization is controlled by a nuclear localization signal-mediated nuclear import via the importin receptor pathway and a nuclear export signal-facilitated nuclear export through a CRM1-dependent pathway. Using the human breast cancer cell line, MCF7, the subcellular distribution of BRCA1 was assessed by immunohistochemical staining and Western blotting analyses of fractionated subcellullar extracts. Ionizing radiation stimulated BRCA1 nuclear export in a dose-dependent manner. This DNA damage-induced BRCA1 nuclear export utilized a CRM1-dependent mechanism and also required wild-type p53, whose function was abrogated by the E6 protein in MCF7 cells. In addition, the dependence on p53 was confirmed using a second cell type operating a tetracycline-inducible system. The effect of ionizing radiation on BRCA1 export was observed in every phase of the cell cycle, although BRCA1 localization did vary between the G(1), S, and G(2)/M phases. These results imply that, in addition to ATM-, ATR-, and Chk2-dependent phosphorylations, cytoplasmic relocalization of BRCA1 protein is a mechanism whereby BRCA1 function is regulated in response to DNA damage.
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Feng
authors.forename: Lisa
authors.initials: L
authors.lastname: Kachnic
authors.forename: Junran
authors.initials: J
authors.lastname: Zhang
authors.forename: Simon N
authors.initials: SN
authors.lastname: Powell
authors.forename: Fen
authors.initials: F
authors.lastname: Xia
mesh_terms: D021581:Active Transport, Cell Nucleus; D019313:BRCA1 Protein / Q000378:metabolism*; D015153:Blotting, Western; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D002470:Cell Survival; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005434:Flow Cytometry; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D028884:Karyopherins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D018160:Receptors, Cytoplasmic and Nuclear; D012190:Retroviridae / Q000235:genetics; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D000097606:Exportin 1 Protein
chemical_list: D019313:BRCA1 Protein; D028884:Karyopherins; D018160:Receptors, Cytoplasmic and Nuclear; D016159:Tumor Suppressor Protein p53; D000097606:Exportin 1 Protein