Butz Nataliya V, Gronostajski Richard M, Campbell Christine E
Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, NY 14214, USA.
Gene. 2006 Aug 1;377:130-9. doi: 10.1016/j.gene.2006.03.016. Epub 2006 Jun 5.
The T-box transcription factor T-bet is expressed in a number of hematopoetic cell types and plays an essential role in the lineage determination of Th1 T-helper cells. In the absence of T-bet, CD4(+) T-cells fail to induce IFNgamma, the cytokine whose expression characterizes Th1 cells. Here we show that, surprisingly, T-bet induces the expression of endogenous IFNgamma in non-immune human cells, including 293 and other cell lines. Thus T-bet can induce IFNgamma expression independently of its role in T-cell lineage determination. In addition, mutations in T-bet, and chimeras of T-bet with other transcription factors including the T-box transcription factor, TBX2, differentially affect the ability of T-bet to activate expression of endogenous IFNgamma versus a T-site regulated reporter gene. A truncated T-betVp16 fusion protein strongly activates the T-site reporter but fails to activate endogenous IFNgamma. Conversely, native T-bet strongly activates endogenous IFNgamma expression but only weakly activates the reporter gene. Fusion of the Vp16 activation domain to full-length T-bet greatly increases its activation of both endogenous IFNgamma and transfected T-site reporter gene expression. In contrast, TBX2Vp16 potently activates the T-site reporter but has a negligible effect on endogenous IFNgamma expression. Butyrate treatment of T-bet expressing cells potentiates the expression of endogenous IFNgamma but weakly represses expression of the T-site reporter gene. These data indicate that induction of endogenous IFNgamma can be uncoupled from differentiation into the Th1 lineage and that the expression of endogenous IFNgamma versus a T-site reporter gene is differentially regulated by T-bet and other T-box proteins.
T 盒转录因子 T-bet 在多种造血细胞类型中表达，在 Th1 辅助性 T 细胞的谱系决定中起关键作用。在缺乏 T-bet 的情况下，CD4(+) T 细胞无法诱导 IFNγ 的产生，而 IFNγ 的表达是 Th1 细胞的特征。令人惊讶的是，我们在此表明 T-bet 可在包括 293 细胞和其他细胞系在内的非免疫人类细胞中诱导内源性 IFNγ 的表达。因此，T-bet 可独立于其在 T 细胞谱系决定中的作用诱导 IFNγ 表达。此外，T-bet 的突变以及 T-bet 与其他转录因子（包括 T 盒转录因子 TBX2）的嵌合体，对 T-bet 激活内源性 IFNγ 表达与 T 位点调控的报告基因表达的能力有不同影响。截短的 T-betVp16 融合蛋白强烈激活 T 位点报告基因，但无法激活内源性 IFNγ。相反，天然 T-bet 强烈激活内源性 IFNγ 表达，但仅微弱激活报告基因。将 Vp16 激活结构域与全长 T-bet 融合可大大增强其对内源性 IFNγ 和转染的 T 位点报告基因表达的激活作用。相比之下，TBX2Vp16 可有效激活 T 位点报告基因，但对内源性 IFNγ 表达的影响可忽略不计。用丁酸盐处理表达 T-bet 的细胞可增强内源性 IFNγ 的表达，但微弱抑制 T 位点报告基因的表达。这些数据表明，内源性 IFNγ 的诱导可与向 Th1 谱系的分化解偶联，并且内源性 IFNγ 与 T 位点报告基因的表达受 T-bet 和其他 T 盒蛋白的不同调控。
