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Coordinate modulation of Sp1, NF‐kappa B, and p53 in confluent human malignant melanoma cells after ionizing radiation
Author(s) -
Yang Chin-Rang,
Wilson-Van Patten Carmell,
Planchon Sarah M.,
Wuerzberger-Davis Shelly M.,
Davis Thomas W.,
Cuthill Scott,
Miyamoto Shigeki,
Boothman David A.
Publication year - 2000
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.14.2.379
Subject(s) - cell cycle , dna damage , biology , cell cycle checkpoint , apoptosis , radioresistance , transfection , genome instability , radiosensitivity , microbiology and biotechnology , retinoblastoma protein , dna repair , cancer research , cell culture , gene , dna , genetics , medicine , radiation therapy
ABSTRACT Regulation of transcriptional responses in growth‐arrested human cells under conditions that promote potentially lethal damage repair after ionizing radiation (IR) is poorly understood. Sp1/retinoblastoma control protein (RCP) DNA binding increased within 30 min and peaked at 2–4 h after IR (450–600 cGy) in confluent radioresistant human malignant melanoma (U1‐Mel) cells. Increased phosphorylation of Sp1 directly corresponded to Sp1/RCP binding and immediate‐early gene induction, whereas pRb remained hypophos‐phorylated. Transfection of U1‐Mel cells with the human papillomavirus E7 gene abrogated Sp1/RCP induction and G 0 /G 1 cell cycle checkpoint arrest responses, increased apoptosis and radiosensitivity, and augmented genetic instability (i.e., increased polyploidy cells) after IR. Increased NF‐κB DNA binding in U1‐Mel cells after IR treatment lasted much longer (i.e., >20 h). U1‐Mel cells overexpressing dominant‐negative IκBα S32/36A mutant protein were significantly more resistant to IR exposure and retained both G 2 /M and G 0 /G 1 cell cycle checkpoint responses without significant genetic instability (i.e., polyploid cell populations were not observed). Nuclear p53 protein levels and DNA binding activity increased only after high doses of IR (>l200 cGy). Disruption of p53 responses in U1‐Mel cells by E6 transfection also abrogated G 0 /G 1 cell cycle checkpoint arrest responses and increased polyploidy after IR, but did not alter radiosensitivity. These data suggest that abrogation of individual components of this coordinate IR‐activated transcription factor response may lead to divergent alterations in cell cycle checkpoints, genomic instability, apoptosis, and survival. Such coordinate transcription factor activation in human cancer cells is reminiscent of prokaryotic SOS responses, and further elucidation of these events should shed light on the initial molecular events in the chromosome instability phenotype.—Yang, C.‐R., Wilson‐Van Patten, C., Planchon, S. M., Wuerzberger‐Davis, S. M., Davis, T. W., Cuthill, C., Miyamoto, S., Boothman, D. A. Coordinate modulation of Sp1, NF‐kappa B, and p53 in confluent human malignant melanoma cells after ionizing radiation. FASEB J. 14, 379–392 (2000)