Rellahan B L, Jensen J P, Howcroft T K, Singer D S, Bonvini E, Weissman A M
Laboratory of Immunobiology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA.
J Immunol. 1998 Mar 15;160(6):2794-801.
In mature T cells, limited synthesis of the TCR-zeta subunit is primarily responsible for regulating surface expression of TCRs. Transcription of zeta is directed by a complex promoter that includes two potential binding sites for the Ets family of transcription factors at -52 (zEBS1) and -135 (zEBS2). Mutation of these two sites results in a marked reduction of transcription from this promoter. Using electrophoretic mobility shift analysis, Elf-1 was demonstrated to be the Ets family member that binds to these sites. One site, zEBS1, matches the optimal Elf-1 consensus sequence in eight of nine bases, making it the best match of any known mammalian Elf-1 binding site. A role for Elf-1 in TCR-zeta trans-activation was confirmed by ectopic expression of Elf-1 in COS-7 cells. This resulted in an increase in TCR-zeta promoter activity that mapped to zEBS1 and zEBS2. Additional support for the involvement of Elf-1 in TCR-zeta trans-activation derives from the finding that a GAL4-Elf-1 fusion protein trans-activated TCR-zeta promoter constructs that had been modified to contain GAL4 DNA binding sites. These results demonstrate that Elf-1 plays an essential role in the trans-activation of a constitutively expressed T cell-specific gene, and that trans-activation occurs in the context of the native promoter in both lymphoid and nonlymphoid cells. Taken together with the existing literature, these data also suggest that the requirement for inducible factors in Elf-1-mediated trans-activation may decrease as the affinity and number of Elf-1 sites increase.
在成熟T细胞中，TCR-ζ亚基的有限合成主要负责调节TCR的表面表达。ζ的转录由一个复杂的启动子指导，该启动子在-52（ζEBS1）和-135（ζEBS2）处包含两个转录因子Ets家族的潜在结合位点。这两个位点的突变导致该启动子的转录显著减少。通过电泳迁移率变动分析，证明Elf-1是与这些位点结合的Ets家族成员。一个位点ζEBS1，在九个碱基中的八个与最佳Elf-1共有序列匹配，使其成为任何已知哺乳动物Elf-1结合位点的最佳匹配。通过在COS-7细胞中异位表达Elf-1，证实了Elf-1在TCR-ζ反式激活中的作用。这导致TCR-ζ启动子活性增加，该活性定位于ζEBS1和ζEBS2。对Elf-1参与TCR-ζ反式激活的进一步支持来自于以下发现：GAL4-Elf-1融合蛋白可反式激活已被修饰以包含GAL4 DNA结合位点的TCR-ζ启动子构建体。这些结果表明，Elf-1在组成性表达的T细胞特异性基因的反式激活中起重要作用，并且反式激活在淋巴样和非淋巴样细胞的天然启动子背景下发生。结合现有文献，这些数据还表明，随着Elf-1位点的亲和力和数量增加，Elf-1介导的反式激活中对诱导因子的需求可能会降低。
