Mitchell T, Sugden B
McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706, USA.
J Virol. 1995 May;69(5):2968-76. doi: 10.1128/JVI.69.5.2968-2976.1995.
The latent membrane protein (LMP) of Epstein-Barr virus contributes to the immortalizing activity of the virus in primary, human B lymphocytes, but its mechanism of function is unknown. LMP is expressed at the plasma membrane and may act by influencing the signalling pathways of infected cells. LMP increases transcription of reporter plasmids that are responsive to members of the NF-kappa B/Rel family of transcription factors (M.-L. Hammarskjold and M. C. Simurda, J. Virol. 66:6496-6501, 1992, and A. Krikos, C. D. Laherty, and V. M. Dixit, J. Biol. Chem. 267:17971-17976, 1992). We measured the stimulation of the activity of a reporter plasmid by LMP in Jurkat and 293 cells in transfection experiments. Expression of LMP stimulated plasmids that contained kappa B enhancer elements but not plasmids that lacked the elements. In 293 cells, expression of the NF-kappa B inhibitor, I kappa B-alpha, reduced the stimulatory activity of LMP. We used deletional analysis to map the domains of LMP that are required for its activity in 293 cells. Wild-type LMP stimulated NF-kappa B by a factor of 20 to 30, while mutant derivatives of LMP that lack oncogenic activity stimulated NF-kappa B by a factor of 3. The multiple membrane-spanning segments together with the carboxy-terminal 55 amino acid residues of LMP were required for its maximal stimulatory function. Residues within its cytoplasmic amino terminus were not required for LMP's stimulation of NF-kappa B. We tested also for stimulation of NF-kappa B activity in cell lines known to support phenotypic changes mediated by expression of LMP. LMP stimulated little NF-kappa B activity in HEp2 cells and no detectable NF-kappa B activity in BALB/3T3 cells. The LMP stimulation of NF-kappa B factors that occurs in some cell lines provides a useful and biochemically tractable assay for determining the function of LMP.
爱泼斯坦-巴尔病毒的潜伏膜蛋白（LMP）有助于该病毒在原代人B淋巴细胞中发挥永生化活性，但其功能机制尚不清楚。LMP在质膜上表达，可能通过影响受感染细胞的信号通路发挥作用。LMP可增加对转录因子NF-κB/Rel家族成员有反应的报告质粒的转录（M.-L. 哈马斯乔尔德和M. C. 西穆尔达，《病毒学杂志》66:6496 - 6501，1992年；以及A. 克里科斯、C. D. 拉赫蒂和V. M. 迪克西特，《生物化学杂志》267:17971 - 17976，1992年）。在转染实验中，我们检测了LMP对Jurkat细胞和293细胞中报告质粒活性的刺激作用。LMP的表达刺激了含有κB增强子元件的质粒，但对缺乏该元件的质粒没有刺激作用。在293细胞中，NF-κB抑制剂IκB-α的表达降低了LMP的刺激活性。我们使用缺失分析来定位LMP在293细胞中发挥活性所需的结构域。野生型LMP刺激NF-κB的倍数为20至30，而缺乏致癌活性的LMP突变衍生物刺激NF-κB的倍数为3。LMP的最大刺激功能需要多个跨膜区段以及其羧基末端的55个氨基酸残基。LMP刺激NF-κB时，其胞质氨基末端的残基并非必需。我们还在已知支持由LMP表达介导的表型变化的细胞系中检测了对NF-κB活性的刺激作用。LMP在HEp2细胞中几乎不刺激NF-κB活性，在BALB/3T3细胞中未检测到可检测到的NF-κB活性。在某些细胞系中发生的LMP对NF-κB因子的刺激作用为确定LMP的功能提供了一种有用且在生物化学上易于处理的检测方法。
