Marcuzzi A, Van Ness B, Rouse T, Lafrenz D
Institute of Human Genetics, University of Minnesota, Minneapolis 55455.
Nucleic Acids Res. 1989 Dec 25;17(24):10455-72. doi: 10.1093/nar/17.24.10455.
Polyclonal activation of murine B cells with bacterial lipopolysaccharide (LPS) and dextran sulfate (DxS) results in cell proliferation as well as increased immunoglobulin gene transcription and antibody secretion. When added to B cell cultures during mitogen activation, anti-mu antibody suppresses the rate of proliferation and immunoglobulin gene expression. Using this model system we show that co-cultures of B cells with LPS/DxS and anti-mu resulted in a decrease of both mu and kappa chain mRNA. Suppression did not prevent B cell entry into cycle nor a significant alteration in the distribution of cells in phases of cell cycle, although it did prolong the cycle transit time in a dose dependent fashion as determined by bromodeoxyuridine pulse labelling. Analysis of B cell specific nuclear binding factors, which previously have been shown to be important in regulating immunoglobulin gene transcription were examined. Results show that the kappa-specific enhancer binding activity of NF-kappa B was induced in activated as well as suppressed cultures. The lymphoid specific factor NF-A2, which recognizes the octamer sequence motif in the promoters of immunoglobulin genes, was induced by the polyclonal activation but was selectively lost in extracts from suppressed cells. Thus, specific regulation of the nuclear factor which plays a critical role in both heavy and light chain immunoglobulin gene expression may contribute to the transcriptional suppression observed in anti-mu treated B cells.
用细菌脂多糖（LPS）和硫酸葡聚糖（DxS）对小鼠B细胞进行多克隆激活，会导致细胞增殖以及免疫球蛋白基因转录和抗体分泌增加。在丝裂原激活期间添加到B细胞培养物中时，抗μ抗体可抑制增殖速率和免疫球蛋白基因表达。利用该模型系统，我们发现B细胞与LPS/DxS和抗μ的共培养导致μ链和κ链mRNA均减少。抑制作用并未阻止B细胞进入细胞周期，也未导致细胞周期各阶段细胞分布的显著改变，尽管通过溴脱氧尿苷脉冲标记确定，它确实以剂量依赖的方式延长了细胞周期转运时间。我们检测了先前已证明在调节免疫球蛋白基因转录中起重要作用的B细胞特异性核结合因子。结果表明，在激活的以及受抑制的培养物中均诱导了NF-κB的κ特异性增强子结合活性。识别免疫球蛋白基因启动子中八聚体序列基序的淋巴细胞特异性因子NF-A2在多克隆激活时被诱导，但在受抑制细胞的提取物中选择性丧失。因此，在重链和轻链免疫球蛋白基因表达中起关键作用的核因子的特异性调节可能有助于在抗μ处理的B细胞中观察到的转录抑制。
