title: Epstein-Barr virus latent membrane protein-1 induction by histone deacetylase inhibitors mediates induction of intercellular adhesion molecule-1 expression and homotypic aggregation.
abstract: Epstein-Barr virus (EBV) latent membrane protein (LMP)-1 induces B lymphocyte immortalization and activates constitutive signal transduction, including NF-kappaB, JNK/p38, and JAK/STAT pathways. During EBV latency, LMP-1 expression induces several B lymphocyte activation markers, including intercellular adhesion molecule (ICAM)-1. We found that various structurally distinct histone deacetylase inhibitors (HDACI), as well as phorbol ester treatment, induced homotypic aggregation in EBV-positive Burkitt's lymphoma lines. Cell-surface expression of ICAM-1 was concurrently strongly up-regulated by both HDACI and phorbol ester treatments. Cell-surface expression of ICAM-1 was concurrently strongly induced by both HDACI and phorbol ester treatment. Among several ICAM family members, only ICAM-1 was up-regulated by both HDACI and phorbol ester treatments, suggesting that up-regulated ICAM-1 expression might mediate the observed increase in homotypic aggregation. HDACI-induced homotypic aggregation was blocked by exposure to a monoclonal antibody specific for the beta-chain (CD18) of an ICAM-1 ligand, LFA-1. Unexpectedly, HDAC inhibition, but not phorbol ester treatment, induced LMP-1 expression in EBV-positive cell lines, and this LMP-1 species was identified by RT-PCR and immunoblot analyses as the latent form of LMP-1. Control of EBV LMP-1 gene expression by HDACI inhibition occurs at the transcriptional level, as indicated by nuclear runoff studies and analysis of steady-state mRNA levels. Dominant-negative LMP-1 efficiently blocked HDACI-induced ICAM-1 up-regulation, and ectopic expression of LMP-1 activated expression of an ICAM-1 promoter-driven reporter gene. The HDACI-induced up-regulation of ICAM-1, and consequent homotypic aggregation, were efficiently blocked by the addition of N-acetyl-L-cysteine and by ectopic expression of a super-repressor IkappaBalpha, while LPM-1 induction was unaffected, suggesting that these effects are mediated by NF-kappaB. We demonstrate, therefore, that the latent isoform of LMP-1 is induced by HDAC inhibition, and that HDACI-induced latent LMP-1 expression, through NF-kappaB activation, is responsible for ICAM-1 expression up-regulation and homotypic adhesion.
authors.affiliation: Cancer Research Center, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
authors.forename: Jae Hong
authors.initials: JH
authors.lastname: Park
authors.forename: Douglas V
authors.initials: DV
authors.lastname: Faller
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D018821:CD18 Antigens / Q000502:physiology; D002449:Cell Aggregation / Q000187:drug effects; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000096:biosynthesis; D016328:NF-kappa B / Q000502:physiology; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic; D014763:Viral Matrix Proteins / Q000235:genetics / Q000502:physiology*; D014775:Virus Activation
chemical_list: D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D016169:Lymphocyte Function-Associated Antigen-1; D016328:NF-kappa B; D014763:Viral Matrix Proteins; D018799:Intercellular Adhesion Molecule-1