TY - JOUR
T1 - When X-ray-inducible proteins meet DNA double strand break repair
AU - Leskov, Konstantin S.
AU - Criswell, Tracy
AU - Antonio, Sheri
AU - Li, Jing
AU - Yang, Chin Rang
AU - Kinsella, Timothy J.
AU - Boothman, David A.
N1 - Funding Information:
From the Department of Human Oncology, University of Wisconsin-Madison, Madison, WI 53792, and Departments of Radiation Oncoloey, Pharmacology, and Patholoey "Molecular Basis of Disease," Case Western Reserve University, Cleveland, Ohio. Address reprint requests to David A. Boothman, Department of Radiation Oncology, Case Western Reserve University, 10900 Euclid Avenue, BRB-326 East, Cleveland, Ohio 44106-4942," E-mail: dab30@po.cwru.edu. This work was published in partial fulfillment of Konstantin Leskov's doctoral degreef rom the Department of Human Oncology, University of Wisconsin-Madison. This work was supported by NIH RO1 grant #CA/ ES578530-1 and by a grant from the DOE, #DE-FGO2-99EQ62724, to D,4.B. Further support for these studies camef rom grants" CA50595 and CA84578 from the NIH (NCI) to T.J.K. Support for this work also came from DOD post-doctoral and pre-doctoral fellowships to K.S.L. (DAMD17/01/1/0196) and T.C. (DAMD17/01/1/0194), respectiv@. Copy@t 0 2001 by W..B. Saunders Cornpary 1053-4296/01/1104-0010535.00/0 doi:10.1053/srao.2001.26912
PY - 2001
Y1 - 2001
N2 - Cellular responses to ionizing radiation (IR) include (a) activation of signal transduction enzymes; (b) stimulation of DNA repair, most notably DNA double strand break (DSB) repair by homologous or nonhomologous recombinatorial pathways; (c) activation of transcription factors and subsequent IR-inducible transcript and protein changes; (d) cell cycle checkpoint delays in G1, S, and G2 required for repair or for programmed cell death of severely damaged cells; (e) activation of zymogens needed for programmed cell death (although IR is a poor inducer of such responses in epithelial cells); and (f) stimulation of IR-inducible proteins that may mediate bystander effects influencing signal transduction, DNA repair, angiogenesis, the immune response, late responses to IR, and possibly adaptive survival responses. The overall response to IR depends on the cell's inherent genetic background, as well as its ability to biochemically and genetically respond to IR-induced damage. To improve the anti-tumor efficacy of IR, our knowledge of these pleiotropic responses must improve. The most important process for the survival of a tumor cell following IR is the repair of DNA double strand breaks (DSBs). Using yeast two-hybrid analyses along with other molecular and cellular biology techniques, we cloned transcripts/proteins that are involved in, or presumably affect, nonhomologous DNA double strand break end-joining (NHEJ) repair mediated by the DNA-PK complex. Using Ku70 as bait, we isolated a number of Ku-binding proteins (KUBs). We identified the first X-ray-inducible transcript/protein (xip8, Clusterin (CLU)) that associates with DNA-PK. A nuclear form of CLU (nCLU) prevented DNA-PK-mediated end joining, and stimulated cell death in response to IR or when overexpressed in the absence of IR. Structure-function analyses using molecular and cellular (including green fluorescence-tagged protein trafficking) biology techniques showed that nCLU appears to be an inactive protein residing in the cytoplasm of epithelial cells. Following IR injury, nCLU levels increase and an as yet undefined posttranslational modification appears to alter the protein, exposing nuclear localization sequences (NLSs) and coiled-coil domains. The modified protein translocates to the nucleus and triggers cell death, presumably through its interaction specifically with Ku70. Understanding nCLU responses, as well as the functions of the KUBs, will be important for understanding DSB repair. Knowledge of DSB repair may be used to improve the antitumor efficacy of IR, as well as other chemotherapeutic agents.
AB - Cellular responses to ionizing radiation (IR) include (a) activation of signal transduction enzymes; (b) stimulation of DNA repair, most notably DNA double strand break (DSB) repair by homologous or nonhomologous recombinatorial pathways; (c) activation of transcription factors and subsequent IR-inducible transcript and protein changes; (d) cell cycle checkpoint delays in G1, S, and G2 required for repair or for programmed cell death of severely damaged cells; (e) activation of zymogens needed for programmed cell death (although IR is a poor inducer of such responses in epithelial cells); and (f) stimulation of IR-inducible proteins that may mediate bystander effects influencing signal transduction, DNA repair, angiogenesis, the immune response, late responses to IR, and possibly adaptive survival responses. The overall response to IR depends on the cell's inherent genetic background, as well as its ability to biochemically and genetically respond to IR-induced damage. To improve the anti-tumor efficacy of IR, our knowledge of these pleiotropic responses must improve. The most important process for the survival of a tumor cell following IR is the repair of DNA double strand breaks (DSBs). Using yeast two-hybrid analyses along with other molecular and cellular biology techniques, we cloned transcripts/proteins that are involved in, or presumably affect, nonhomologous DNA double strand break end-joining (NHEJ) repair mediated by the DNA-PK complex. Using Ku70 as bait, we isolated a number of Ku-binding proteins (KUBs). We identified the first X-ray-inducible transcript/protein (xip8, Clusterin (CLU)) that associates with DNA-PK. A nuclear form of CLU (nCLU) prevented DNA-PK-mediated end joining, and stimulated cell death in response to IR or when overexpressed in the absence of IR. Structure-function analyses using molecular and cellular (including green fluorescence-tagged protein trafficking) biology techniques showed that nCLU appears to be an inactive protein residing in the cytoplasm of epithelial cells. Following IR injury, nCLU levels increase and an as yet undefined posttranslational modification appears to alter the protein, exposing nuclear localization sequences (NLSs) and coiled-coil domains. The modified protein translocates to the nucleus and triggers cell death, presumably through its interaction specifically with Ku70. Understanding nCLU responses, as well as the functions of the KUBs, will be important for understanding DSB repair. Knowledge of DSB repair may be used to improve the antitumor efficacy of IR, as well as other chemotherapeutic agents.
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U2 - 10.1053/srao.2001.26912
DO - 10.1053/srao.2001.26912
M3 - Article
C2 - 11677660
AN - SCOPUS:0034798920
VL - 11
SP - 352
EP - 372
JO - Seminars in Radiation Oncology
JF - Seminars in Radiation Oncology
SN - 1053-4296
IS - 4
ER -