Interleukin-2 transcription is regulated in vivo at the level of coordinated binding of both constitutive and regulated factors.
Interleukin-2 transcription is regulated in vivo at the level of coordinated binding of both constitutive and regulated factors.
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Interleukin-2 转录在体内在组成型因子和调节因子协调结合的水平上受到调节。
DOI：
10.1128/mcb.14.3.2159-2169.1994
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发表时间：
1994
影响因子：
5.3
通讯作者：
Wold,BJ
中科院分区：
文献类型：
--
作者：
Garrity,PA;Chen,D;Rothenberg,EV;Wold,BJ
白细胞介素-2 （IL-2）的转录发育局限于T细胞，并且在生理上依赖于特定的刺激，如抗原识别。先前的研究表明，这种严格的双层调控是通过转录启动子/增强子DNA片段介导的，该片段由多种识别元件组成。结合其中一些元素的因子在许多细胞类型中都存在，而其他因子则是信号依赖性的，T细胞特异性的，或两者兼而有之。这就提出了关于调控IL-2表达的分子机制的几个问题。在信号依赖诱导之前，可用因子和IL-2增强子之间的稳定相互作用是否反映了T细胞的发育承诺？在哪个水平上，因子与DNA结合或因子活性一旦结合，天然增强子内的单个调控元件受到调控？考虑到许多相对非特异性因素的参与，发育和生理特异性是通过什么机制来实现的？为了回答这些问题，我们使用了体内足迹来确定和比较细胞环境中天然IL-2位点的蛋白质- dna相互作用模式，包括表达不同IL-2 dna结合因子亚群的EL4 t淋巴瘤细胞和32D克隆5前肥大细胞。我们还使用免疫抑制剂环孢素A作为药理学试剂，进一步剖析环孢素A敏感因子在蛋白质- dna复合物的组装和维持中所起的作用。所有位点类型的占用仅在T细胞中观察到，然后仅在信号转导途径的激发下观察到。即使在32D克隆5号前肥大细胞中显示存在部分重叠的il -2结合活性亚群，这也是正确的。这一观察结果在32D细胞中尤其引人注目，因为在信号刺激下，它们调动了大量的IL-2 dna结合活性，这是通过体外核提取物测定的。我们得出结论，除了T细胞激活外，所有类别的结合活性都不能稳定地占据其在IL-2中的同源位点，并且IL-2转录的特异性在染色体占用水平上被强制执行，这似乎是一个全有或全无的现象。
Interleukin-2 (IL-2) transcription is developmentally restricted to T cells and physiologically dependent on specific stimuli such as antigen recognition. Prior studies have shown that this stringent two-tiered regulation is mediated through a transcriptional promoter/enhancer DNA segment which is composed of diverse recognition elements. Factors binding to some of these elements are present constitutively in many cell types, while others are signal dependent, T cell specific, or both. This raises several questions about the molecular mechanism by which IL-2 expression is regulated. Is the developmental commitment of T cells reflected molecularly by stable interaction between available factors and the IL-2 enhancer prior to signal-dependent induction? At which level, factor binding to DNA or factor activity once bound, are individual regulatory elements within the native enhancer regulated? By what mechanism is developmental arid physiological specificity enforced, given the participation of many relatively nonspecific elements? To answer these questions, we have used in vivo footprinting to determine and compare patterns of protein-DNA interactions at the native IL-2 locus in cell environments, including EL4 T-lymphoma cells and 32D clone 5 premast cells, which express differing subsets of IL-2 DNA-binding factors. We also used the immunosuppressant cyclosporin A as a pharmacological agent to further dissect the roles played by cyclosporin A-sensitive factors in the assembly and maintenance of protein-DNA complexes. Occupancy of all site types was observed exclusively in T cells and then only upon excitation of signal transduction pathways. This was true even though partially overlapping subsets of IL-2-binding activities were shown to be present in 32D clone 5 premast cells. This observation was especially striking in 32D cells because, upon signal stimulation, they mobilized a substantial set of IL-2 DNA-binding activities, as measured by in vitro assays using nuclear extracts. We conclude that binding activities of all classes fail to stably occupy their cognate sites in IL-2, except following activation of T cells, and that specificity of IL-2 transcription is enforced at the level of chromosomal occupancy, which appears to be an all-or-nothing phenomenon.