Feederle R, Neuhierl B, Baldwin G, Bannert H, Hub B, Mautner J, Behrends U, Delecluse H J
German Cancer Research Center, ATV-F100, Im Neuenheimer Feld 242, 69120 Heidelberg, Germany.
J Virol. 2006 Oct;80(19):9435-43. doi: 10.1128/JVI.00473-06.
Epstein-Barr virus (EBV) is a tumor virus with marked B lymphotropism. After crossing the B-cell membrane, the virus enters cytoplasmic vesicles, where decapsidation takes place to allow transfer of the viral DNA to the cell nucleus. BNRF1 has been characterized as the EBV major tegument protein, but its precise function is unknown. We have constructed a viral mutant that lacks the BNRF1 gene and report here its in vitro phenotype. A recombinant virus devoid of BNRF1 (DeltaBNRF1) showed efficient DNA replication and production of mature viral particles. B cells infected with the DeltaBNRF1 mutant presented viral lytic antigens as efficiently as B cells infected with wild-type or BNRF1 trans-complemented DeltaBNRF1 viruses. Antigen presentation in B cells infected with either wild-type (EBV-wt) or DeltaBNRF1 virus was blocked by leupeptin addition, showing that both viruses reach the endosome/lysosome compartment. These data were confirmed by direct observation of the mutant virus in endosomes of infected B cells by electron microscopy. However, we observed a 20-fold reduction in the number of B cells expressing the nuclear protein EBNA2 after infection with a DeltaBNRF1 virus compared to wild-type infection. Likewise, DeltaBNRF1 viruses transformed primary B cells much less efficiently than EBV-wt or BNRF1 trans-complemented viruses. We conclude from these findings that BNRF1 plays an important role in viral transport from the endosomes to the nucleus.
爱泼斯坦-巴尔病毒（EBV）是一种具有显著B淋巴细胞嗜性的肿瘤病毒。病毒穿过B细胞膜后，进入细胞质囊泡，在那里发生脱壳，使病毒DNA转移到细胞核。BNRF1已被鉴定为爱泼斯坦-巴尔病毒的主要被膜蛋白，但其确切功能尚不清楚。我们构建了一个缺失BNRF1基因的病毒突变体，并在此报告其体外表型。一种缺乏BNRF1的重组病毒（DeltaBNRF1）显示出高效的DNA复制和成熟病毒颗粒的产生。感染DeltaBNRF1突变体的B细胞呈现病毒裂解抗原的效率与感染野生型或BNRF1反式互补DeltaBNRF1病毒的B细胞一样高。添加亮抑酶肽可阻断感染野生型（EBV-wt）或DeltaBNRF1病毒的B细胞中的抗原呈递，表明这两种病毒都能到达内体/溶酶体区室。通过电子显微镜直接观察感染B细胞内体中的突变病毒证实了这些数据。然而，我们观察到，与野生型感染相比，感染DeltaBNRF1病毒后表达核蛋白EBNA2的B细胞数量减少了20倍。同样，DeltaBNRF1病毒转化原代B细胞的效率远低于EBV-wt或BNRF1反式互补病毒。我们从这些发现中得出结论，BNRF1在病毒从内体到细胞核的转运中起重要作用。
