Arulampalam V, Furebring C, Samuelsson A, Lendahl U, Borrebaeck C, Lundkvist I, Pettersson S
Department of Biosciences, Karolinska Institute, NOVUM, 141 57 Huddinge, Sweden.
Int Immunol. 1996 Jul;8(7):1149-57. doi: 10.1093/intimm/8.7.1149.
To delineate the role of the IgH 3' enhancer in the regulation of Ig heavy (IgH) chain gene expression, mice harbouring rearranged IgH transgenes, with (PSVmu3) and without (PSVmu1) this element, were produced. RNA and protein analysis from the different transgenic lines revealed a 5- to 7-fold increase in the expression level of the transgene containing the IgH 3' enhancer. This difference is also reflected at the protein level in hybridomas generated from the two transgenic lines. The elevation of transgene Ig expression in the PSVmu3 lines is restricted to activated B lymphocytes, an observation which is further supported by the ability of this transgene to be reactivated upon immunization. Interestingly, although the up-regulation of transgene expression in PSVmu3 animals is considerably higher in comparison to the PSVmu1 animals, a significant response is still observed in the PSVmu1 mice. We speculate therefore that the IgH locus is subject to transcriptional modification in late B cell development. Our data suggest that both the Emu enhancer and the IgH 3' enhancer can up-regulate transgene Ig expression, but the presence of the 3' enhancer results in elevated levels of transgene Ig production. It therefore appears that the expression level of IgH genes is subject to transcriptional modification during B cell development. Additional control elements are most likely required for optimal Ig expression, since our expression data from the transgene in PSVmu3 animals are incompatible with endogenous Ig levels. The recent identification of additional enhancer elements in the far 3' end of the IgH locus supports this possibility. The data presented here provides a sound basis for the production of high levels of mAb, possibly tailored to suit the needs of the researcher.
为了阐明免疫球蛋白重链（IgH）3'增强子在Ig重链基因表达调控中的作用，我们构建了携带重排IgH转基因的小鼠，其中一些（PSVmu3）带有该元件，另一些（PSVmu1）则没有。对不同转基因系的RNA和蛋白质分析显示，含有IgH 3'增强子的转基因表达水平提高了5至7倍。这种差异在由这两个转基因系产生的杂交瘤的蛋白质水平上也有体现。PSVmu3系中转基因Ig表达的升高仅限于活化的B淋巴细胞，这一观察结果得到了该转基因在免疫后能够重新激活的能力的进一步支持。有趣的是，尽管与PSVmu1动物相比，PSVmu3动物中转基因表达的上调幅度要高得多，但在PSVmu1小鼠中仍观察到显著的反应。因此，我们推测IgH基因座在B细胞发育后期会发生转录修饰。我们的数据表明，Emu增强子和IgH 3'增强子都可以上调转基因Ig的表达，但3'增强子的存在会导致转基因Ig产生水平升高。因此，似乎IgH基因的表达水平在B细胞发育过程中会受到转录修饰。最佳的Ig表达很可能还需要其他控制元件，因为我们从PSVmu3动物中的转基因获得的表达数据与内源性Ig水平不相符。最近在IgH基因座远3'端发现的其他增强子元件支持了这种可能性。本文提供的数据为生产高水平的单克隆抗体提供了坚实的基础，这些抗体可能经过定制以满足研究人员的需求。
