c-Jun-NH2 terminal kinase (JNK)-mediates AP-1 activation by thioredoxin: phosphorylation of cJun, JunB, and Fra-1.
Thioredoxin (Trx) is a small ubiquitous protein, which has been shown to be involved in redox-dependent cellular functions. In this article, we demonstrate that the increased level of Trx induces AP-1 DNA binding in a redox-dependent manner by activating JNK subgroup of MAPKs. The majority of AP-1 DNA binding complex was found to be composed of cJun, JunB, and Fra-1. Increased expression of Trx resulted in phosphorylation of cJun, Jun B, and Fra-1. Further, increased expression of Trx induced the phosphorylation of MKK4 and MKK7 which are upstream kinases of the JNK signaling cascade. In co-transfection studies, AP-1-dependent luciferase reporter vector and pcDNA3-Trx increased luciferase activity demonstrating that increased expression of Trx increases AP-1 transactivation. In addition, dominant-negative JNK kinase (dnJNK/MKK4) or dominant-negative JNK (dnJNK) inhibited Trx-mediated AP-1 transactivation, as well as AP-1 DNA binding. Furthermore, transfection of kinase-dead MEKK1, an initiating kinase of the JNK pathway inhibited Trx-mediated AP-1 transactivation and DNA binding, suggesting that MEKK1 may mediate Trx-induced AP-1 activation. In contrast, wild-type MEKK1 overexpression did not inhibit Trx-mediated AP-1 activation. Taken together, our data demonstrate that increased expression of Trx induces MKK4/MKK7-dependent JNK activation, resulting in enhanced DNA binding, and transactivation of AP-1 transcription factor.
Das
Kumuda C
KC
Department of Pathology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. kdas@uams.edu
Muniyappa
Harish
H
D004247:DNA / Q000378:metabolism; D017930:Genes, Reporter / Q000187:drug effects; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000819:agonists* / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured; D000099169:Fos-Related Antigen 1
D004247:DNA; D048031:JNK Mitogen-Activated Protein Kinases; D008156:Luciferases; D020930:MAP Kinase Kinase Kinases; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D013879:Thioredoxins; D018808:Transcription Factor AP-1; D000099169:Fos-Related Antigen 1