Bories J C, Demengeot J, Davidson L, Alt F W
Unité 93, Institut National de la Santé et de la Recherche Médicale,Hôpital Saint-Louis, Paris, France.
Proc Natl Acad Sci U S A. 1996 Jul 23;93(15):7871-6. doi: 10.1073/pnas.93.15.7871.
To assess the role of transcriptional enhancers in regulating accessibility of the T-cell receptor beta-chain (TCRbeta) locus, we generated embryonic stem cell lines in which a single allelic copy of the endogenous TCRbeta enhancer (Ebeta) was either deleted or replaced with the immunoglobulin heavy-chain intronic enhancer. We assayed the effects of these mutations on activation of the TCRbeta locus in normal T- and B-lineage cells by RAG-2 (recombination-activating gene 2)-deficient blastocyst complementation. We found that Ebeta is required for rearrangement and germ-line transcription of the TCRbeta locus in T-lineage cells. In the absence of Ebeta, the heavy-chain intronic enhancer partially supported joining region beta-chain rearrangement in T- but not in B-lineage cells. However, ability of the heavy-chain intronic enhancer to induce rearrangements was blocked by linkage to an expressed neomycin-resistance gene (neo(r)). These results demonstrate a critical role for Ebeta in promoting accessibility of the TCRbeta locus and suggest that additional negative elements may cooperate to further modulate this process.
为了评估转录增强子在调节T细胞受体β链（TCRβ）基因座可及性中的作用，我们构建了胚胎干细胞系，其中内源性TCRβ增强子（Eβ）的单个等位基因拷贝被删除或被免疫球蛋白重链内含子增强子取代。我们通过RAG-2（重组激活基因2）缺陷型囊胚互补实验，检测了这些突变对正常T细胞和B细胞系中TCRβ基因座激活的影响。我们发现Eβ是T细胞系细胞中TCRβ基因座重排和种系转录所必需的。在没有Eβ的情况下，重链内含子增强子部分支持T细胞系细胞而非B细胞系细胞中连接区β链重排。然而，重链内含子增强子诱导重排的能力被与表达的新霉素抗性基因（neo(r)）的连锁所阻断。这些结果证明了Eβ在促进TCRβ基因座可及性方面的关键作用，并表明可能有其他负性元件协同作用以进一步调节这一过程。
