The Effect of Epstein-Barr Virus LMP1 on DNA Repair in Human Epithelial Cells

• Main Authors: Yi-Ren Chen, 陳逸人
• Other Authors: Jen-Yang Chen
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/00790033119525584422

碩士 === 國立臺灣大學 === 微生物學研究所 === 91 === Chromosome aberrations are closely related to tumor formation and it is believed that virus infection may cause cellular transformation by interfering DNA repair system. Cytogenetic studies have shown that there are many chromosomal abnormalities in the tissues of EBV-associated malignancies. It suggests that EBV infection may induce genomic instability and further contribute to the carcinogenesis. Latent membrane protein 1（LMP1） is essential for EBV-mediated B cell transformation. LMP1 displays potent oncogenic properties in rodent fibroblasts and induces a wide range of effects in B cells and epithelial cells. LMP1 functions as a constitutively active tumor necrosis factor receptor（TNFR）engaging many signaling pathways including NFkB, JNK, p38 and JAK/STAT1 pathways. In this study, we used host cell reactivation（HCR）assay to investigate the effect of LMP1 on DNA repair in human epithelial cells. In HCR assay, LMP1 reduced the ability of DNA repair in different cells and this effect was dose-dependent. LMP1 also repressed the p53- or p21-induced DNA repair. To determine which domain of LMP1 is important for reducing DNA repair, different LMP1 deletion mutants were used in HCR assay. LMP1 mutant lacking CTAR1 domain lost its ability in reducing DNA repair. A P204xQ206xT208 motif in CTAR1 is crucial for TRAFs binding to trigger downstream signal pathway. LMP1 mutant substituted Pro204 and Thr208 with Ala also lost its ability in reducing DNA repair. This indicates a P204xQ206xT208 motif of CTAR1 domain is important for LMP1 to interfere DNA repair. Furthermore, to investigate which LMP1-induced pathway is associated with DNA repair, we established stable cell lines expressing dominant negative mutants of IkB (IkBDN) or TRAF2 (TRAF2D87). In IkBDN expressing cells, LMP1 still maintained the suppressing ability. In TRAF2D87 expressing cells, however, LMP1 lost the suppressing ability. Besides, LMP1 sensitized cells upon UV exposure and this effect was also related to CTAR1 domain. Taken together, we understand that LMP1 represses DNA repair in human epithelial cells by binding TRAF2 to its CTAR1 domain. However, the exact mechanism or involving signal pathway is still needed to solve.