title: EBV-LMP1-targeted DNAzyme induces DNA damage and causes cell cycle arrest in LMP1-positive nasopharyngeal carcinoma cells.
abstract: This study aimed to determine the molecular mechanisms underlying the effect of the LMP1-targeted DNAzyme 1 (DZ1) on cell cycle progression in nasopharyngeal carcinoma (NPC) cells. We showed that the active DZ1 inhibited the expression of latent membrane protein 1 (LMP1) and induced a G1 phase arrest. In addition, this cell cycle deregulation was shown to be accompanied by upregulation of the DNA damage marker γ-H2AX, downregulation of the DNA damage response factor p-p53-Ser15 and cell proliferation inhibition. To investigate what affected the cell cycle progression, we examined the expression of two checkpoint-related cyclins and cyclin-dependent kinases (CDKs). We found a decrease of cyclin D1 and cyclin E protein levels at 24 h from the DZ1 treatment. Moreover, we observed inhibition of CDK4 activity and decreased cyclin D1 expression in the complexes immunoprecipitated with CDK4 antibody. We also found a reduction in cdc2 phosphorylation at Thr161 which partially stands for the cdc2 kinase activity in DZ1-treated CNE1-LMP1 cells, although the downregulation of LMP1 expression had no effect on the cyclin B1 and cdc2 expression. Further, we analyzed changes in cdc2 kinase activity induced by DZ1 and found that the downregulation of the LMP1 expression resulted in a 5-fold reduction in cdc2 kinase activity in CNE1-LMP1. The data suggest that the downregulation of the LMP1 expression by DZ1 was able to induce DNA damage, which then further inhibited the cell proliferation and resulted in malfunction of cell cycle checkpoints that led to G1 phase arrest and the decrease in number of cells in G2/M phase.
authors.affiliation: Cancer Research Institute, Xiangya School of Medicine, Central South University, Changsha, Hunan 410078, P.R. China.
authors.forename: Xiaoqian
authors.initials: X
authors.lastname: Ma
authors.forename: Zhijie
authors.initials: Z
authors.lastname: Xu
authors.forename: Lifang
authors.initials: L
authors.lastname: Yang
authors.forename: Lanbo
authors.initials: L
authors.lastname: Xiao
authors.forename: Min
authors.initials: M
authors.lastname: Tang
authors.forename: Jingchen
authors.initials: J
authors.lastname: Lu
authors.forename: San
authors.initials: S
authors.lastname: Xu
authors.forename: Yiping
authors.initials: Y
authors.lastname: Tang
authors.forename: Xinxian
authors.initials: X
authors.lastname: Wen
authors.forename: Xingming
authors.initials: X
authors.lastname: Deng
authors.forename: Lunquan
authors.initials: L
authors.lastname: Sun
authors.forename: Ya
authors.initials: Y
authors.lastname: Cao
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D016203:CDC2 Protein Kinase; D002277:Carcinoma; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D059447:Cell Cycle Checkpoints; D049109:Cell Proliferation; D019926:Cyclin B / Q000378:metabolism; D019938:Cyclin D1 / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D018844:Cyclin-Dependent Kinases; D004249:DNA Damage; D021881:DNA, Catalytic / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006657:Histones / Q000378:metabolism; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D015513:Oncogene Proteins / Q000378:metabolism; D010766:Phosphorylation; D014407:Tumor Cells, Cultured; D014763:Viral Matrix Proteins / Q000378:metabolism*
chemical_list: C530104:CCND1 protein, human; C475820:CCNE1 protein, human; D019926:Cyclin B; D019927:Cyclin E; D021881:DNA, Catalytic; C037662:EBV-associated membrane antigen, Epstein-Barr virus; C468783:H2AX protein, human; D006657:Histones; D015513:Oncogene Proteins; D014763:Viral Matrix Proteins; D019938:Cyclin D1; D016203:CDC2 Protein Kinase; C528899:CDK1 protein, human; D018844:Cyclin-Dependent Kinases