Chen N N, Kerr D, Chang C F, Honjo T, Khalili K
Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Gene. 1997 Jan 31;185(1):55-62. doi: 10.1016/s0378-1119(96)00630-0.
Glial factor 1 (GF-1) is a partial cDNA isolated from a human brain cDNA library which encodes a truncated protein with binding ability to the B-regulatory domain of the human neurotropic virus, JCV. GF-1 exhibits sequence homology to the central region of the newly identified human DNA-binding protein S(mu)bp-2. GF-1 appears to be a partial cDNA for human S(mu)bp-2 based on its sequence homology to S(mu)bp-2 and their chromosomal co-localization. In this report, we have employed transfection assay and have compared the ability of GF-1 and its full-length form, S(mu)bp-2, on regulating the activity of JCV promoters in glial cells. Our results demonstrate that, unlike GF-1 which stimulates JCV early promoter in glial cells, overexpression of S(mu)bp-2 exhibits no drastic effect on the transcription of the viral early promoter. The activity of the viral late promoter was noticeably increased by both GF-1 and S(mu)bp-2, although the level of induction by GF-1 was consistently higher than that detected by S(mu)bp-2. Use of deletion constructs in co-transfection assay revealed that the B-domain of the JCV promoter is required for transcriptional activation by GF-1 and S(mu)bp-2. Expression of GF-1 and S(mu)bp-2 in glial cells increased the induced level of JCV late gene transcription by the viral early protein, T-antigen. Examination of the viral DNA replication by DpnI assay indicated that, unlike GF-1, S(mu)bp-2 has the ability to decrease the level of JCV DNA replication in glial cells. These observations suggest that the N-terminal portion of S(mu)bp-2 which encompasses several helicase motifs and/or its C-terminus, both of which are missing in GF-1, may confer differential effects on viral gene transcription and replication. The biological importance of our findings in regulation of the JCV lytic cycle in glial cells is discussed.
神经胶质因子1（GF-1）是从人脑cDNA文库中分离得到的部分cDNA，它编码一种截短的蛋白质，该蛋白质对人嗜神经病毒JCV的B调节域具有结合能力。GF-1与新鉴定的人DNA结合蛋白S（μ）bp-2的中央区域表现出序列同源性。基于GF-1与S（μ）bp-2的序列同源性及其染色体共定位，GF-1似乎是人类S（μ）bp-2的部分cDNA。在本报告中，我们采用了转染试验，并比较了GF-1及其全长形式S（μ）bp-2在调节神经胶质细胞中JCV启动子活性方面的能力。我们的结果表明，与在神经胶质细胞中刺激JCV早期启动子的GF-1不同，S（μ）bp-2的过表达对病毒早期启动子的转录没有显著影响。GF-1和S（μ）bp-2均显著增加了病毒晚期启动子的活性，尽管GF-1的诱导水平始终高于S（μ）bp-2检测到的水平。在共转染试验中使用缺失构建体表明，JCV启动子的B结构域是GF-1和S（μ）bp-2转录激活所必需的。GF-1和S（μ）bp-2在神经胶质细胞中的表达增加了病毒早期蛋白T抗原诱导的JCV晚期基因转录水平。通过DpnI试验检测病毒DNA复制表明，与GF-1不同，S（μ）bp-2具有降低神经胶质细胞中JCV DNA复制水平的能力。这些观察结果表明，S（μ）bp-2的N末端部分包含几个解旋酶基序和/或其C末端（这两者在GF-1中均缺失）可能对病毒基因转录和复制产生不同的影响。我们讨论了这些发现对神经胶质细胞中JCV裂解周期调节的生物学重要性。
