| Summary: | 碩士 === 慈濟大學 === 生命科學系碩士班 === 102 === Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA1) is pervasively expressed in all types of EBV associated malignancies. It maintains viral episome and promotes transcription through binding to the latent origin of EBV, oriP. It has been previously identified the Gly-Arg-rich region between amino acids 325 and 376 of EBNA1 can be methylated by protein ariginine methyltransferase (PRMT) 1 or 5, suggesting PRMTs may have a role in regulation of EBNA1 functions. In this study, we demonstrated plasmid expressing PRTM 8 potentially up-regulated the EBNA1/oriP dependent reporter activity while neither ectopic expression of other PRMTs (1-7) was shown to affect the EBNA1/oriP dependent reporter activity, suggesting a new role of PRMT 8 in EBNA1 mediated transcriptional enhancement. PRMT8 is a type I PRMT, whose expression tends to be localized at plasma membrane and induced in brain. Despite knowing it has a role in post-translational modification the knowledge with respect to the importance of PRMT8 for cell functions remains to be elucidated. We found the expression of PRMT 8 is highly induced at both protein and RNA levels in EBV transformed lymphoblastoid cell lines (LCL) but not EBV negatively infected B lymphoma cells (BJAB). Similar PRMT 8 expressing patterns were also verified in EBNA1 or EBNA2 stably expressed BJAB cell line but not seen in the BJAB cells bearing stably expressed latency associated membrane protein 1 (LMP1). In agreement with our findings, the expression of EBNA1 or EBNA2 alone is sufficient to induce the luciferase activity of PRMT 8 promoter reporter by 2 to 4 –fold. When dissecting the role of PRMT 8 in EBNA1/oriP dependent transcription, neither the membrane localizing mutant (G2A) nor the catalytic mutant (E194Q) was shown to potentiate EBNA1/oriP dependent luciferase activity. Interestingly, we found the automethylation mutant R58K elicited hypermorphic effects on EBNA1/oriP dependent reporter activity, whereas the mutant R58F that was designed to mimic the increased hydrophobicity of a methylated arginine did not cause the hypermophic effects on EBNA1/oriP reporter activity. Taken together, we identified PRMT 8 is specifically induced in EBV infected lymphoblastoid cells and the role of this novel PRMT8 in EBNA1/oriP dependent transcription.
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