Repression of Smad-dependent transforming growth factor-beta signaling by Epstein-Barr virus latent membrane protein 1 through nuclear factor-kappaB.
EBV-encoded LMP-1 is absolutely required for EBV transformation of cells. Previous studies showed that LMP-1 is responsible for mediating resistance to the anti-proliferative effects of TGF-beta that characterizes EBV-transformed cells. To clarify the mechanisms of resistance to TGF-beta by LMP-1, we examined the effect of expression of LMP-1 on the activity of TGF-beta-responsive promoters. Interestingly, LMP-1 inhibited TGF-beta-responsive promoters activity despite lack of direct interaction of LMP-1 and Smad proteins, intracellular signaling molecules in the TGF-beta signal transduction pathway. Although TGF-beta treatment increased the expression of p15, TGF-beta-induced gene, this effect was counteracted by expression of LMP-1. The repressive effect was mapped to the NF-kappaB activation domains in the cytoplasmic carboxyl terminus of LMP-1. Furthermore, LMP-1-mediated inhibition of TGF-beta-responsive promoter was markedly restored after inhibition of NF-kappaB activity. LMP-1 failed to affect receptor-dependent formation of heteromers containing Smad proteins as well as the DNA-binding activity of Smad proteins. Overexpression of the transcriptional coactivator CBP and p300 abrogated the inhibitory effect of LMP-1 on the TGF-beta-responsive promoter. Our results suggest that LMP-1 represses the TGF-beta signaling through the NF-kappaB signaling pathway at transcriptional level by competing for a limited pool of transcriptional coactivators. These results enhance our understanding of the molecular mechanisms of viral pathogenesis in EBV-associated malignancies.
Mori
Naoki
N
Department of Virology, Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan. n-mori@med.u-ryukyu.ac.jp
Morishita
Mariko
M
Tsukazaki
Tomoo
T
Yamamoto
Naoki
N
D000818:Animals; D001667:Binding, Competitive; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D018797:Cell Cycle Proteins / Q000096:biosynthesis; D002460:Cell Line; D002472:Cell Transformation, Viral / Q000502:physiology*; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000502:physiology*; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D019942:Genes, p16; D004854:Herpesvirus 4, Human / Q000235:genetics / Q000502:physiology*; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics / Q000502:physiology; D008113:Liver Neoplasms / Q000473:pathology; D008168:Lung; D008907:Mink; D008957:Models, Genetic; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015398:Signal Transduction; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors*; D025521:Tumor Suppressor Proteins; D014763:Viral Matrix Proteins / Q000502:physiology*
C493966:CDKN2B protein, human; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004268:DNA-Binding Proteins; C037662:EBV-associated membrane antigen, Epstein-Barr virus; C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D009687:Nuclear Proteins; D018125:Receptors, Transforming Growth Factor beta; D011993:Recombinant Fusion Proteins; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D025521:Tumor Suppressor Proteins; D014763:Viral Matrix Proteins; D000072000:NF-KappaB Inhibitor alpha; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II