RelA is a potent transcriptional activator of the CD28 response element within the interleukin 2 promoter.
T-cell activation requires two different signals. The T-cell receptor's recognition of a specific antigen on antigen-presenting cells provides one, and the second signal comes from costimulatory molecules such as CD28. In contrast, T cells that are stimulated with antigen in the absence of the CD28 costimulatory signal can become anergic (nonresponsive). The CD28 response element (CD28RE) has been identified as the DNA element mediating interleukin 2 (IL-2) gene activation by CD28 costimulation. Our previous work demonstrates that the Rel/NF-kappa B family proteins c-Rel, RelA (p65), and NFKB1 (p50) are involved in the complex that binds to the CD28RE. We also showed that c-Rel, but not NFKB1 (p50), can bind to the CD28RE and activate CD28RE-driven transcription in cotransfection assays. However, the role of RelA (p65) in CD28 signaling has not yet been addressed. We provide evidence that RelA (p65) itself bound directly to the CD28RE of the IL-2 promoter and other lymphokine promoters. In addition, RelA (p65) was a potent transcriptional activator of the CD28RE in vivo. We show that a RelA (p65)-c-Rel heterodimer bound to the CD28RE and synergistically activated the CD28RE enhancer activity. We also demonstrate that activated Raf-1 kinase synergized with RelA (p65) in activating the CD28RE enhancer activity. Interestingly, a soluble anti-CD28 monoclonal antibody alone, in the absence of other stimuli, also synergized with RelA (p65) in activating the CD28RE. Furthermore, we show that RelA (p65) activated expression of the wild-type IL-2 promoter but not the CD28RE-mutated IL-2 promoter. A combination of RelA (p65) and NFKB1 (p50) also activated the IL-2 promoter through the CD28RE site. These results demonstrate the functional regulation of the CD28RE, within the IL-2 promoter, by Rel/NF-kappa B transcription factors.
Lai
J H
JH
Department of Microbiology and Immunology, Baylor College of Medicine, Houston, Texas 77030, USA.
Horvath
G
G
Subleski
J
J
Bruder
J
J
Ghosh
P
P
Tan
T H
TH
D001483:Base Sequence; D018106:CD28 Antigens / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000494:pharmacology; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics; D006801:Humans; D020672:I-kappa B Proteins; D007371:Interferon-gamma / Q000235:genetics; D007376:Interleukin-2 / Q000096:biosynthesis / Q000235:genetics*; D007377:Interleukin-3 / Q000235:genetics; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000502:physiology*; D051996:Transcription Factor RelA; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation
D018106:CD28 Antigens; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D007376:Interleukin-2; D007377:Interleukin-3; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D051996:Transcription Factor RelA; D000072000:NF-KappaB Inhibitor alpha; D007371:Interferon-gamma; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf