title: Activation of DNA methyltransferase 1 by EBV LMP1 Involves c-Jun NH(2)-terminal kinase signaling.
abstract: EBV latent membrane protein 1 (LMP1) activates cellular DNA methyltransferases, resulting in hypermethylation and silencing of E-cadherin. However, the underlying mechanism remains to be elucidated. In this study, we show that LMP1 directly induces the dnmt1 promoter activity through its COOH-terminal activation region-2 YYD domain. Using (i) LMP1 mutants, (ii) dominant negative mutants c-jun NH(2)-terminal kinase (JNK)-DN, p38-DN, and constitutive active mutant IkappaB, as well as (iii) dsRNAs targeting c-Jun, JNK, and tumor necrosis factor receptor-associated death domain protein, and (iv) signal transduction inhibitors, we show that LMP1-mediated DNA methyltransferase-1 (DNMT1) activation involves JNK but not nuclear factor kappaB and p38/mitogen-activated protein kinase signaling. In addition, LMP1 is unable to activate dnmt1-P1 promoter with activator protein-1 (AP-1) site mutation. Chromatin immunoprecipitation assay results also confirm that LMP1 activates P1 promoter via the JNK-AP-1 pathway. Furthermore, chromatin immunoprecipitation assay data in LMP1-inducible cells disclose that LMP1 induces formation of a transcriptional repression complex, composed of DNMT1 and histone deacetylase, which locates on E-cadherin gene promoter. Treatment with JNK inhibitor, SP600125, prevents the formation of this repression complex. Statistical analyses of the immunohistochemical staining of 32 nasopharyngeal carcinoma (NPC) biopsies show LMP1 expression (18 of 32, 56.25%), DNMT1 expression (31 of 32, 97%), and phospho-c-Jun (27 of 32, 84.38%), suggesting that overexpression of these proteins is observed in NPC tumor. Overall, these results support a mechanistic link between JNK-AP-1 signaling and DNA methylation induced by the EBV oncogene product LMP1.
authors.affiliation: Graduate Institute of Basic Medical Sciences and Pathology Core, Chang-Gung Molecular Medicine Research Center, Chang-Gung University, Taiwan, Republic of China.
authors.forename: Chia-Lung
authors.initials: CL
authors.lastname: Tsai
authors.forename: Hsin-Pai
authors.initials: HP
authors.lastname: Li
authors.forename: Yen-Jung
authors.initials: YJ
authors.lastname: Lu
authors.forename: Chuen
authors.initials: C
authors.lastname: Hsueh
authors.forename: Ying
authors.initials: Y
authors.lastname: Liang
authors.forename: Chi-Long
authors.initials: CL
authors.lastname: Chen
authors.forename: Sai Wah
authors.initials: SW
authors.lastname: Tsao
authors.forename: Ka-Po
authors.initials: KP
authors.lastname: Tse
authors.forename: Jau-Song
authors.initials: JS
authors.lastname: Yu
authors.forename: Yu-Sun
authors.initials: YS
authors.lastname: Chang
mesh_terms: D015820:Cadherins / Q000235:genetics; D002460:Cell Line; D045744:Cell Line, Tumor; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism*; D017930:Genes, Reporter; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D014763:Viral Matrix Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D015820:Cadherins; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D014763:Viral Matrix Proteins; D004248:DNA (Cytosine-5-)-Methyltransferases; D048031:JNK Mitogen-Activated Protein Kinases