Safak Mahmut, Sadowska Beata, Barrucco Robert, Khalili Kamel
Laboratory of Molecular Neurovirology, Center for Neurovirology and Cancer Biology, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122, USA.
J Virol. 2002 Apr;76(8):3828-38. doi: 10.1128/jvi.76.8.3828-3838.2002.
Human polyomavirus JC virus (JCV) is a causative agent of progressive multifocal leukoencephalopathy which results from lytic infection of glial cells. Although significant progress has been made in understanding the regulation of JCV gene transcription, the mechanism(s) underlying the viral lytic cycle remains largely unknown. We recently reported that the JCV late auxiliary Agnoprotein may have a regulatory role in JCV gene transcription and replication. Here, we investigated its regulatory function in viral gene transcription through its physical and functional interaction with YB-1, a cellular transcription factor which contributes to JCV gene expression in glial cells. Time course studies revealed that Agnoprotein is first detected at day 3 postinfection and that its level increased during the late stage of the infection cycle. Agnoprotein is mainly localized to the cytoplasmic compartment of the infected cell, with high concentrations found in the perinuclear region. While the position of Agnoprotein throughout the infection cycle remained relatively unaltered, the subcellular distribution of YB-1 between the cytoplasm and nucleus changed. Results from coimmunoprecipitation and glutathione S-transferase pull-down experiments revealed that Agnoprotein physically interacts with YB-1 and that the amino-terminal region of Agnoprotein, between residues 1 and 36, is critical for this association. Further investigation of this interaction by functional assays demonstrated that Agnoprotein negatively regulates YB-1-mediated gene transcription and that the region corresponding to residues 1 to 36 of Agnoprotein is important for the observed regulatory event. Taken together, these data demonstrate that the interaction of the viral late regulatory Agnoprotein and cellular Y-box binding factor YB-1 modulates transcriptional activity of JCV promoters.
人类多瘤病毒 JC 病毒（JCV）是进行性多灶性白质脑病的病原体，该疾病由神经胶质细胞的裂解性感染引起。尽管在理解 JCV 基因转录调控方面取得了重大进展，但病毒裂解周期的潜在机制在很大程度上仍然未知。我们最近报道，JCV 晚期辅助蛋白 Agnoprotein 可能在 JCV 基因转录和复制中具有调节作用。在此，我们通过其与 YB-1 的物理和功能相互作用研究了它在病毒基因转录中的调节功能，YB-1 是一种细胞转录因子，有助于在神经胶质细胞中表达 JCV 基因。时间进程研究表明，Agnoprotein 在感染后第 3 天首次被检测到，并且其水平在感染周期后期增加。Agnoprotein 主要定位于受感染细胞的细胞质区室，在核周区域发现高浓度。虽然在整个感染周期中 Agnoprotein 的位置保持相对不变，但 YB-1 在细胞质和细胞核之间的亚细胞分布发生了变化。免疫共沉淀和谷胱甘肽 S-转移酶下拉实验结果表明，Agnoprotein 与 YB-1 发生物理相互作用，并且 Agnoprotein 的 1 至 36 位残基之间的氨基末端区域对于这种关联至关重要。通过功能测定对这种相互作用的进一步研究表明，Agnoprotein 负调节 YB-1 介导的基因转录，并且与 Agnoprotein 的 1 至 36 位残基相对应的区域对于观察到的调节事件很重要。综上所述，这些数据表明病毒晚期调节蛋白 Agnoprotein 与细胞 Y 盒结合因子 YB-1 的相互作用调节了 JCV 启动子的转录活性。
