Chen U, Scheuermann R H, Wirth T, Gerster T, Roeder R G, Harshman K, Berger C
Basel Institute for Immunology, Switzerland.
Nucleic Acids Res. 1991 Nov 11;19(21):5981-9. doi: 10.1093/nar/19.21.5981.
Stimulation of small, resting, splenic B cells with bacterial lipopolysaccharide (LPS) induces proliferation, differentiation to plasma cell formation, and the expression of immunoglobulin heavy chain (IgH). When this is combined with agents which crosslink surface Ig, differentiation and the induction of surface immunoglobulin are suppressed even though proliferation proceeds. We find that anti-mu antibodies suppresses Ig gene expression of transfected mu constructs, even if either the membrane or secretory segments have been deleted. We examined the effects of anti-mu treatment on the IgH enhancer (IgHE) attached to a heterologous test gene (CAT). Indeed the IgH enhancer alone was subject to anti-mu suppression, while the SV40 enhancer was insensitive. To determine what was responsible for suppression of enhancer function by anti-mu we examined nuclear extracts from stimulated splenic B cells for the presence of sequence-specific DNA binding activities to various sites within the enhancer. We found two specific differences--an induction in mu E5 binding activity, and a reduction in octamer transcription factor 2 (OTF2) binding activity, after anti-mu treatment. Analysis of these cells by in situ immunofluorescence with anti-OTF2 antibodies suggests that the nuclear localization of OTF2 in anti-mu treated cells may change, as well as its absolute level.
用细菌脂多糖（LPS）刺激小型、静止的脾B细胞可诱导其增殖、分化形成浆细胞以及免疫球蛋白重链（IgH）的表达。当这与交联表面Ig的试剂联合使用时，即使增殖仍在进行，分化和表面免疫球蛋白的诱导也会受到抑制。我们发现抗μ抗体可抑制转染的μ构建体的Ig基因表达，即使膜段或分泌段已被缺失。我们研究了抗μ处理对连接到异源测试基因（CAT）的IgH增强子（IgHE）的影响。实际上，单独的IgH增强子会受到抗μ抑制，而SV40增强子则不敏感。为了确定抗μ抑制增强子功能的原因，我们检测了来自受刺激脾B细胞的核提取物中与增强子内各个位点的序列特异性DNA结合活性。我们发现了两个特定差异——抗μ处理后，μE5结合活性增加，八聚体转录因子2（OTF2）结合活性降低。用抗OTF2抗体进行原位免疫荧光分析这些细胞表明，抗μ处理细胞中OTF2的核定位及其绝对水平可能会发生变化。
