Stimulation of c-Rel transcriptional activity by PKA catalytic subunit beta.
Nuclear factor kappaB (NF-kappaB) is a eukaryotic transcription factor which responds to different extracellular signals. It is involved in immune response, inflammation, and cell proliferation. Increased expression of c-Rel (or its viral homolog v-Rel), one component of the NF-kappaB factors, induces tumorigenesis in different systems. The activity of NF-kappaB can be regulated by protein kinase A (PKA) in a cAMP-independent manner. Our previous results showed that c-MYC induces the activity of PKA by inducing the transcription of the gene encoding the PKA catalytic subunit beta (PKA-Cbeta). Constitutive expression of PKA-Cbeta in Rat1a cells induces their transformation. Here we show that CREB is unlikely to be a phosphorylation target of PKA-Cbeta as characterized by different cell lines. Electrophoretic mobility shift assays showed that c-Rel is present as a significant component of the NF-kappaB factors in c-MYC overexpressing status. The transcriptional activity of c-Rel was significantly stimulated by PKA-Cbeta. Coactivators p300/CBP are at least partially responsible for the enhanced activation mediated by c-Rel and PKA-Cbeta. Interaction between c-Rel and PKA-Cbeta was demonstrated using coimmunoprecipitation assays. Immunoprecipitation-in vitro phosphorylation assays showed the direct phosphorylation of c-Rel by PKA-Cbeta. These results indicate that c-Rel is a reasonable phosphorylation target of PKA-Cbeta, and that the transcriptional activity of c-Rel is stimulated by PKA-Cbeta possibly through the interaction with p300/CBP.
Yu
Shih-Hung
SH
Institute of Biochemistry, National Yang-Ming University, Taipei 112, Taiwan.
Chiang
Wei-Chung
WC
Shih
Hsiu-Ming
HM
Wu
Kou-Juey
KJ
D000818:Animals; D002460:Cell Line; D016384:Consensus Sequence; D000242:Cyclic AMP / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D050881:E1A-Associated p300 Protein; D017930:Genes, Reporter; D016259:Genes, myc; D020573:Genes, rel; D047468:Immunoprecipitation; D007527:Isoenzymes / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism; D009687:Nuclear Proteins / Q000502:physiology; D010766:Phosphorylation; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis; D020569:Proto-Oncogene Proteins c-rel / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015534:Trans-Activators / Q000502:physiology; D014158:Transcription, Genetic; D014162:Transfection
D017362:Cyclic AMP Response Element-Binding Protein; D007527:Isoenzymes; D016328:NF-kappa B; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; D020569:Proto-Oncogene Proteins c-rel; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D000242:Cyclic AMP; D050881:E1A-Associated p300 Protein; C494362:Ep300 protein, rat; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; D017868:Cyclic AMP-Dependent Protein Kinases; C463959:protein kinase A Calpha