Regulation of SRC-3 (pCIP/ACTR/AIB-1/RAC-3/TRAM-1) Coactivator activity by I kappa B kinase.
In the past few years, many nuclear receptor coactivators have been identified and shown to be an integral part of receptor action. The most frequently studied of these coactivators are members of the steroid receptor coactivator (SRC) family, SRC-1, TIF2/GRIP1/SRC-2, and pCIP/ACTR/AIB-1/RAC-3/TRAM-1/SRC-3. In this report, we describe the biochemical purification of SRC-1 and SRC-3 protein complexes and the subsequent identification of their associated proteins by mass spectrometry. Surprisingly, we found association of SRC-3, but not SRC-1, with the I kappa B kinase (IKK). IKK is known to be responsible for the degradation of I kappa B and the subsequent activation of NF-kappa B. Since NF-kappa B plays a key role in host immunity and inflammatory responses, we therefore investigated the significance of the SRC-3-IKK complex. We demonstrated that SRC-3 was able to enhance NF-kappa B-mediated gene expression in concert with IKK. In addition, we showed that SRC-3 was phosphorylated by the IKK complex in vitro. Furthermore, elevated SRC-3 phosphorylation in vivo and translocation of SRC-3 from cytoplasm to nucleus in response to tumor necrosis factor alpha occurred in cells, suggesting control of subcellular localization of SRC-3 by phosphorylation. Finally, the hypothesis that SRC-3 is involved in NF-kappa B-mediated gene expression is further supported by the reduced expression of interferon regulatory factor 1, a well-known NF-kappa B target gene, in the spleens of SRC-3 null mutant mice. Taken together, our results not only reveal the IKK-mediated phosphorylation of SRC-3 to be a regulated event that plays an important role but also substantiate the role of SRC-3 in multiple signaling pathways.
Wu
Ray-Chang
RC
Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Qin
Jun
J
Hashimoto
Yoshihiro
Y
Wong
Jiemin
J
Xu
Jianming
J
Tsai
Sophia Y
SY
Tsai
Ming-Jer
MJ
O'Malley
Bert W
BW
D000123:Acetyltransferases; D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D020169:Caspases / Q000378:metabolism; D002458:Cell Fractionation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D051548:Histone Acetyltransferases; D006801:Humans; D051550:I-kappa B Kinase; D050856:Interferon Regulatory Factor-1; D046911:Macromolecular Substances; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D056920:Nuclear Receptor Coactivator 1; D056921:Nuclear Receptor Coactivator 3; D015513:Oncogene Proteins; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015534:Trans-Activators / Q000302:isolation & purification / Q000378:metabolism*; D014157:Transcription Factors / Q000302:isolation & purification / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; C494258:Irf1 protein, mouse; D046911:Macromolecular Substances; D016328:NF-kappa B; D015513:Oncogene Proteins; D010750:Phosphoproteins; D015534:Trans-Activators; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D000123:Acetyltransferases; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538866:NCOA3 protein, human; C538861:Ncoa1 protein, mouse; C538867:Ncoa3 protein, mouse; D056920:Nuclear Receptor Coactivator 1; D056921:Nuclear Receptor Coactivator 3; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; D020169:Caspases