Thioredoxin nuclear translocation and interaction with redox factor-1 activates the activator protein-1 transcription factor in response to ionizing radiation.
Thioredoxin (TRX) is a cytoplasmic, redox-sensitive signaling factor believed to participate in the regulation of nuclear transcription factors mediating cellular responses to environmental stress. Activation of the activator protein (AP)-1 transcription factor is thought to be mediated in part by redox-sensitive interactions between the nuclear signaling protein redox factor-1 (Ref-1) and TRX. In this study, the role of TRX and Ref-1 in the activation of the AP-1 complex was examined in HeLa and Jurkat cell lines exposed to ionizing radiation (IR). After exposure to IR, nuclear levels of immunoreactive TRX increased, accompanied by an increase in AP-1 DNA binding activity. It was shown that a physical interaction between Ref-1 and TRX occurs within the nucleus and is enhanced after exposure to IR. Furthermore, TRX immunoprecipitated from irradiated cells was capable of activating AP-1 DNA binding activity in nonirradiated nuclear extracts. In addition, immunodepletion of Ref-1 from nuclear extracts demonstrated that the increase in AP-1 DNA binding activity after IR was also dependent upon the presence of Ref-1 from irradiated cells. Finally, the ability of both TRX and Ref-1 from irradiated cells to stimulate AP-1 DNA binding in nonirradiated nuclear extracts was abolished by chemical oxidation and restored by chemical reduction. These results indicate that, in response to IR, TRX and Ref-1 undergo changes in redox state that contribute to the activation of AP-1 DNA binding activity. These experiments suggest that a redox-sensitive signaling pathway leading from TRX to Ref-1 to the AP-1 complex participates in the up-regulation of DNA binding activity in response to ionizing radiation.
Wei
S J
SJ
Section of Cancer Biology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri 63108, USA.
Botero
A
A
Hirota
K
K
Bradbury
C M
CM
Markovina
S
S
Laszlo
A
A
Spitz
D R
DR
Goswami
P C
PC
Yodoi
J
J
Gius
D
D
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D019556:COS Cells; D019757:Carbon-Oxygen Lyases / Q000276:immunology / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism / Q000528:radiation effects; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism / Q000528:radiation effects; D004247:DNA / Q000378:metabolism; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D006367:HeLa Cells; D006801:Humans; D010084:Oxidation-Reduction / Q000528:radiation effects; D015398:Signal Transduction / Q000528:radiation effects*; D013879:Thioredoxins / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism*
D000906:Antibodies; D018808:Transcription Factor AP-1; D013879:Thioredoxins; D004247:DNA; D019757:Carbon-Oxygen Lyases; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase