Henson J, Saffer J, Furneaux H
Laboratory of Molecular Neuro-oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
Ann Neurol. 1992 Jul;32(1):72-7. doi: 10.1002/ana.410320112.
JC virus is a human DNA virus that specifically infects oligodendroglial cells, resulting in a demyelinating disease (progressive multifocal leukoencephalopathy) of the central nervous system of immunosuppressed patients. The host-range restriction of JC virus is controlled at the level of viral gene transcription. To analyze further the determinants of glial specificity, we cloned and sequenced the JC viral early promoter elements directly from the infected brain tissue of four patients. The promoter of each isolate contained a novel identical sequence, 5'-AGGGAGGAGC (GA box), located immediately upstream of the TATA box. This GA box is not present in the original isolate of JC virus (Mad-1 strain), which was obtained after numerous passages in tissue culture. The GA box has 80% homology with the consensus binding site for the transcription factor Sp1. Using a gel retardation assay, we found that Sp1 binds to the GA box. Alteration of bases within the sequence abolished binding of Sp1, demonstrating sequence specificity of binding. Immunohistochemical localization of Sp1 expression in human brain reveals that expression is restricted to the nuclei of oligodendroglial cells, cerebellar basket cells, and endothelial cells. The GA box is present in the promoters of the myelin basic protein and proteolipid protein genes. On the basis of these observations, we suggest that this Sp1-like binding site participates in the control of glial-specific gene expression.
JC病毒是一种人类DNA病毒，它特异性感染少突胶质细胞，导致免疫抑制患者中枢神经系统发生脱髓鞘疾病（进行性多灶性白质脑病）。JC病毒的宿主范围限制在病毒基因转录水平受到控制。为了进一步分析神经胶质特异性的决定因素，我们直接从四名患者的感染脑组织中克隆并测序了JC病毒早期启动子元件。每个分离株的启动子都包含一个新的相同序列，5'-AGGGAGGAGC（GA框），位于TATA框的紧邻上游。这个GA框在JC病毒的原始分离株（Mad-1株）中不存在，该分离株是在组织培养中多次传代后获得的。GA框与转录因子Sp1的共有结合位点有80%的同源性。使用凝胶阻滞试验，我们发现Sp1与GA框结合。序列内碱基的改变消除了Sp1的结合，证明了结合的序列特异性。Sp1在人脑表达的免疫组织化学定位显示，表达仅限于少突胶质细胞、小脑篮状细胞和内皮细胞的细胞核。GA框存在于髓鞘碱性蛋白和蛋白脂蛋白基因的启动子中。基于这些观察结果，我们认为这个类似Sp1的结合位点参与了神经胶质特异性基因表达的控制。
