Klein S, Gerster T, Picard D, Radbruch A, Schaffner W
Nucleic Acids Res. 1985 Dec 20;13(24):8901-12. doi: 10.1093/nar/13.24.8901.
A transcriptional enhancer is thought to play a major role in determining tissue-specific expression of the immunoglobulin heavy chain (IgH) gene (1-3). However in three B-lymphoid cell lines the Ig enhancer has been lost due to a spontaneous deletion, yet heavy chain synthesis persists at a high level (4-6). In the case of the enhancerless delta chain gene (5) we wanted to test whether the IgH enhancer is no longer necessary for maintenance of transcription or whether perhaps a new enhancer was created de novo by the deletion process. To this end we have cloned the relevant portion of the variant IgH gene and transfected it into myeloma and hybridoma cells. We find that the reintroduced gene segment is not expressed unless it is linked again to an enhancer. The results suggest that the IgH enhancer is necessary for the onset of transcription, presumably by organizing the gene into stable transcription complexes, but is dispensable at later stages once the transcription unit is activated.
转录增强子被认为在决定免疫球蛋白重链（IgH）基因的组织特异性表达中起主要作用（1-3）。然而，在三种B淋巴细胞系中，Ig增强子由于自发缺失而丢失，但重链合成仍维持在高水平（4-6）。对于无增强子的δ链基因（5），我们想测试IgH增强子对于维持转录是否不再必要，或者是否可能通过缺失过程重新产生了一个新的增强子。为此，我们克隆了变异IgH基因的相关部分，并将其转染到骨髓瘤细胞和杂交瘤细胞中。我们发现，重新导入的基因片段除非再次与增强子相连，否则不会表达。结果表明，IgH增强子对于转录起始是必要的，大概是通过将基因组织成稳定的转录复合物，但一旦转录单元被激活，在后期阶段它是可有可无的。
