Repression of Smad-dependent transforming growth factor-beta signaling by Epstein-Barr virus latent membrane protein 1 through nuclear factor-kappaB

Int J Cancer. 2003 Jul 10;105(5):661-8. doi: 10.1002/ijc.11146.

Abstract

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.

MeSH terms

  • Animals
  • Binding, Competitive
  • Carcinoma, Hepatocellular / pathology
  • Cell Cycle Proteins / biosynthesis
  • Cell Line
  • Cell Transformation, Viral / physiology*
  • Cyclin-Dependent Kinase Inhibitor p15
  • Cyclin-Dependent Kinase Inhibitor p16 / biosynthesis
  • DNA-Binding Proteins / physiology*
  • Gene Expression Regulation, Viral*
  • Genes, Reporter
  • Genes, p16
  • Herpesvirus 4, Human / genetics
  • Herpesvirus 4, Human / physiology*
  • Humans
  • I-kappa B Proteins / genetics
  • I-kappa B Proteins / physiology
  • Liver Neoplasms / pathology
  • Lung
  • Mink
  • Models, Genetic
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / metabolism*
  • Nuclear Proteins / biosynthesis
  • Nuclear Proteins / genetics
  • Nuclear Proteins / physiology
  • Promoter Regions, Genetic
  • Protein Serine-Threonine Kinases
  • Receptor, Transforming Growth Factor-beta Type II
  • Receptors, Transforming Growth Factor beta / physiology
  • Recombinant Fusion Proteins / physiology
  • Signal Transduction
  • Smad2 Protein
  • Smad3 Protein
  • Smad4 Protein
  • Trans-Activators / biosynthesis
  • Trans-Activators / genetics
  • Trans-Activators / physiology*
  • Transcription, Genetic*
  • Transfection
  • Transforming Growth Factor beta / antagonists & inhibitors*
  • Tumor Suppressor Proteins*
  • Viral Matrix Proteins / physiology*

Substances

  • CDKN2B protein, human
  • Cell Cycle Proteins
  • Cyclin-Dependent Kinase Inhibitor p15
  • Cyclin-Dependent Kinase Inhibitor p16
  • DNA-Binding Proteins
  • EBV-associated membrane antigen, Epstein-Barr virus
  • I kappa B beta protein
  • I-kappa B Proteins
  • NF-kappa B
  • NFKBIA protein, human
  • Nuclear Proteins
  • Receptors, Transforming Growth Factor beta
  • Recombinant Fusion Proteins
  • SMAD2 protein, human
  • SMAD3 protein, human
  • SMAD4 protein, human
  • Smad2 Protein
  • Smad3 Protein
  • Smad4 Protein
  • Trans-Activators
  • Transforming Growth Factor beta
  • Tumor Suppressor Proteins
  • Viral Matrix Proteins
  • NF-KappaB Inhibitor alpha
  • Protein Serine-Threonine Kinases
  • Receptor, Transforming Growth Factor-beta Type II