A multiprotein complex consisting of the cellular coactivator p300, AP-1/ATF, as well as NF-kappaB is responsible for the activation of the mouse major histocompatibility class I (H-2K(b)) enhancer A.
Major histocompatibility complex (MHC) class I genes encode highly polymorphic antigens that play an essential role in a number of immunological processes. Their expression is activated in response to a variety of signals and is mediated through several promoter elements among which the enhancer A is one of the key control regions. It contains binding sites for several transcription factors, for example: (i) a well-characterized binding site for rel/NF-kappaB transcription factors in its 3'-end (the H2TF1 or kappaB1 element), (ii) a second kappaB site (the kappaB2 element), which is located immediately adjacent 5' to the H2TF1 element and which is recognized by p65/relA in the human HLA system, and (iii) an AP-1/ATF recognition sequence in the 5' end (EnA-TRE). Here we demonstrate that latter element is bound by at least two distinct heterodimers of the AP-1/ATF transcription factor family, namely c-Jun/ATF-2 and c-Jun/Fra2. Moreover, our data reveal that the enhancer A is simultaneously bound by AP-1/ATF and rel/NF-kappaB transcription factors and that the cellular coactivator p300, which enhances enhancer A-driven reporter gene expression if cotransfected, is recruited to the enhancer A through this multiprotein complex. In contrast to the complete enhancer A, neither the EnA-TRE nor the H2TF1 element on their own are able to confer activation on a heterologous promoter in response to the phorbol ester tumor promoter TPA or the cytokine TNFalpha. Moreover, deletion of any one of the enhancer A control elements results in a dramatic loss of its inducibility by TNFalpha, and point mutations in either the EnA-TRE or the H2TF1 element lead to the loss of AP-1/ATF or NF-kappaB binding, respectively, and to the loss of enhancer A inducibility. Therefore, we conclude that the enhancer A is synergistically activated through a multiprotein complex containing AP-1/ATF, NF-kappaB transcription factors as well as the cellular coactivator p300.
Brockmann
D
D
Institute of Molecular Biology (Cancer Research), University of Essen Medical School, Germany. dieter.brockmann@uni-essen.de
Pützer
B M
BM
Lipinski
K S
KS
Schmücker
U
U
Esche
H
H
D051696:Activating Transcription Factors; D000818:Animals; D001798:Blood Proteins / Q000378:metabolism*; D050882:CREB-Binding Protein; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D006183:H-2 Antigens / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D052003:NF-kappa B p52 Subunit; D009687:Nuclear Proteins / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015534:Trans-Activators / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology
D051696:Activating Transcription Factors; D001798:Blood Proteins; D006183:H-2 Antigens; D016328:NF-kappa B; D052003:NF-kappa B p52 Subunit; D009687:Nuclear Proteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D015500:Chloramphenicol O-Acetyltransferase; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; C494364:Crebbp protein, mouse; D013755:Tetradecanoylphorbol Acetate