The Epstein-Barr virus latent membrane protein-1 (LMP1) mediates activation of NF-kappa B and cell surface phenotype via two effector regions in its carboxy-terminal cytoplasmic domain.
The Epstein-Barr virus (EBV) encoded latent membrane protein, LMP1, is oncogenic in rodent fibroblasts and is an essential effector protein in EBV-induced growth-transformation of human B lymphocytes. Previous structure-function studies with LMP1 have relied largely on rodent fibroblast transformation as a functional readout, with apparently conflicting results. We have now analysed several LMP1 mutants in various human cell types, including B cells, T cells and epithelial cells, using two independent functional assays; (i) activation of NF-kappa B, and (ii) induction of two cell surface activation markers, CD54 and CD40. The results suggest that the cytosolic N-terminus is not essential for LMP1 function in any cell type studied. The third and fourth transmembrane helices and the intracytosolic loops are dispensable for activation of NF-kappa B, but they do influence the induction of CD54 and CD40. The major effector domain appears to be the cytosolic C-terminus in which were identified two 'C-terminal activating regions', CTAR-1 (residues 194-232) and CTAR-2 (residues 351-386). Whilst the exact results depended upon the host cell line, CTAR-2 was generally more important for activation of NF-kappa B, and both CTAR-1 and CTAR-2 were required for optimal induction of CD54 and CD40. Analysis of NF-kappa B activation by LMP1 in Rat-1 fibroblasts indicated that many mutations that were functional in human cells were poorly tolerated in the rodent cells; a result that is in broad agreement with published Rat-1 transformation data.
Huen
D S
DS
Institute for Cancer Studies, University of Birmingham Medical School, UK.
Henderson
S A
SA
Croom-Carter
D
D
Rowe
M
M
D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis*; D000956:Antigens, Viral / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D002460:Cell Line; D002522:Chlorocebus aethiops; D004854:Herpesvirus 4, Human / Q000502:physiology*; D006801:Humans; D016130:Immunophenotyping; D008969:Molecular Sequence Data; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism*; D051381:Rats; D013329:Structure-Activity Relationship; D014162:Transfection; D014407:Tumor Cells, Cultured; D014763:Viral Matrix Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*
D015703:Antigens, CD; D000956:Antigens, Viral; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D016328:NF-kappa B; D014763:Viral Matrix Proteins