Egr-2 and Egr-3 are negative regulators of T cell activation

T cell receptor engagement in the absence of proper accessory signals leads to T cell anergy. E3 ligases are involved in maintaining the anergic state. However, the specific molecules responsible for the induction of anergy have yet to be elucidated. Using microarray analysis we have identified here early growth response gene 2 (Egr-2) and Egr-3 as key negative regulators of T cell activation. Overexpression of Egr2 and Egr3 was associated with an increase in the E3 ubiquitin ligase Cbl-b and inhibition of T cell activation. Conversely, T cells from Egr3(-/-) mice had lower expression of Cbl-b and were resistant to in vivo peptide-induced tolerance. These data support the idea that Egr-2 and Egr-3 are involved in promoting a T cell receptor-induced negative regulatory genetic program.     

Transcriptional activation of the IL31 gene by NFAT and STAT6

IL-31, a newly identified member of the IL-6 cytokine family, is involved in many pathological conditions, including atopic dermatitis and pruritis. In this study, we investigated how expression of IL-31 is regulated in T cells and mast cells. We observed that expression of IL-31 required a calcium signal and was dependent on the calcineurin-NFAT signaling pathway. Moreover, we found that IL-31 promoter contains a positive regulatory region that mediates calcium- and IL-4-dependent induction of the IL-31 gene and demonstrated that a change into an open chromatin conformation occurs in this region after stimulation with calcium and IL-4. Whereas IL-4 responsiveness required STAT6 binding sites, calcium responsiveness of IL-31 promoter required NFAT binding sites that bind NFATc1 and NFATc2 in vitro and in vivo. The induction of IL-31 promoter activity was impaired when these sites were mutated but was enhanced by CA-NFATc1 or STAT6 proteins and further increased synergistically by combinations of both proteins. Furthermore, the importance of STAT6 proteins was indicated by impaired, IL-4-mediated induction of IL-31 in STAT6-diminished Jurkat cells. Thus, our data demonstrate that calcium and IL-4 signals are required to mediate induction of IL-31 in Th2 cells and mast cells and that this induction appears to result from specific binding of NFAT and STAT6 proteins.     

人Egr-1启动子的克隆及其在肿瘤细胞中的辐射诱导反应

目的:克隆人Egr-1基因的启动子, 插入荧光素酶报告基因载体中, 并检测电离辐射对其活性的影响.方法:采用PCR技术从人乳腺癌细胞系MCF-7基因组中扩增出Egr-1启动子, 将其克隆到pGL3-basic载体中;将重组质粒转染人肿瘤细胞, 测定Egr-1启动子在不同辐射条件下转录活性的改变.结果:成功构建了Egr-1启动子的荧光素酶报告基因;在不同剂量的γ射线照射后, Egr-1的启动子活性均明显高于未照射组;在同一剂量照射后48 h, Egr-1的启动子活性达峰值.结论:本实验构建的Egr-1启动子具有辐射激活的功能, 为进一步研究放射-基因治疗奠定了基础.