Characterization of Epstein-Barr Virus BVRF1 Gene Product

• Main Authors: Ting-Yau Lee, 李廷曜
• Other Authors: 許翠瑛
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/59177155683396668117

碩士 === 臺灣大學 === 微生物學研究所 === 95 === Epstein-Barr virus (EBV) BVRF1 was recognized as a capsid-associated tegument protein through the sequence homology with the Herpes simplex virus type 1 (HSV-1) UL25 gene. It was demonstrated previously that UL25 protein is required for encapsidation but not for cleavage of replicated viral DNA. In addition, the UL25 of pseudorabies virus (PrV) which also belongs to α-herpersvirus family also was shown to play an important role on nuclear export of viral nucleocapsides. The observation from yeast two-hybrid assay indicated that BVRF1 could interact with BGLF4 (protein kinase), BFRF1 and BFLF2. The BFRF1 and BFLF2 proteins were identified to be necessary for efficient viral envelopment at the nuclear membrane. Recent study also indicated that BGLF4 might be involved in the egress of viral nucleocapsids. Taken together with the analogy to the crucial roles of other viral UL25 and findings from yeast two-hybrid assay, we wondered whether BVRF1 might play an important role in the encapsidation of EBV. Despite that, the expression and biological function of BVRF1 have not been characterized. In this study, the expression kinetics and subcellular localization of BVRF1 products were detected in EBV-positive epithelial and B cells upon induction of lytic cycle by using BVRF1-specific mouse antibodies. BVRF1 is expressed in both the nuclei and cytoplasm of EBV-positive NA cells. The promoter activity of BVRF1 is regulated mainly by the immediate-early transcription activator Rta. Furthermore, HA-BVRF1 was shown to interact with endogenous BFRF1 and BGLF4 in EBV positive NA cells undergoing lytic viral replication by co-immunoprecipitation assays. In addition, the higher molecular mass of HA-BVRF1 was observed in SDS-PAGE analysis when BGLF4 was coexpressed in HeLa cells, suggesting HA-BVRF1 could be a potential subtract of BGLF4 protein kinase. Overall, we suggest the BVRF1 may participate in viral encapsidation and egress of viral nucleocapsids.