title: Nucleocytoplasmic shuttling of BID is involved in regulating its activities in the DNA-damage response.
abstract: The BH3-only BID protein acts as a sentinel to interconnect specific death signals to the core apoptotic pathway. Our previous data demonstrated that BID is important for both S-phase arrest and cell death following DNA damage, and that the cell cycle arrest function is regulated by its phosphorylation by the ATM kinase. We also showed that a portion of cellular BID localizes to the nucleus. Here, we demonstrate that etoposide and ionizing radiation induce the exit of BID from the nucleus and that leptomycin B, a specific inhibitor of the nuclear export receptor CRM1, prevents the nuclear exit of BID. BID carries a nuclear export signal (NES) consensus motif; however, it does not seem to be functional. To examine the importance of BID nuclear export, we targeted BID to the nucleus by fusing it to a strong nuclear localization signal (NLS). NLS-BID is phosphorylated in a similar time course as wild-type BID, but does not exit the nucleus following etoposide treatment. Importantly, introducing NLS-BID into BID(-/-) cells failed to restore S-phase arrest and cell death in response to etoposide. These results implicate BID as a nuclear protein and raise the possibility that nucleocytoplasmic shuttling of BID is involved in regulating its activities in the DNA-damage response.
authors.affiliation: Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: G
authors.initials: G
authors.lastname: Oberkovitz
authors.forename: L
authors.initials: L
authors.lastname: Regev
authors.forename: A
authors.initials: A
authors.lastname: Gross
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D004249:DNA Damage; D005047:Etoposide / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018613:Microscopy, Confocal; D019913:Nuclear Localization Signals; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016196:S Phase / Q000187:drug effects
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D019913:Nuclear Localization Signals; D011993:Recombinant Fusion Proteins; D005047:Etoposide; D020169:Caspases