Molecular cloning of cDNAs for transcriptional factors of indoleamine 2,3-dioxygenase induced by IFN-gamma

本研究的目的是表征参与IFN-γ介导的吲哚胺2，3-双加氧酶（IDO），色氨酸降解酶的诱导的转录因子。直到1994年，我们在所有的人培养细胞系中发现了两种IDO mRNA，1.7kb和2.3kb，它们在5'端的侧翼区大小不同。mRNA诱导的动力学和IDO基因表达的5'控制区的分析表明：1）两种mRNA的诱导都被蛋白质合成的抑制剂阻断，表明需要从头合成蛋白质因子，2）蛋白质合成在加入IFN-γ后3小时内发生，3）含有IRF-1元件的1.7kb mRNA的5'区，ISRE元件、Y-box和X-box，但对IDO mRNA的转录没有IFN-γ应答性促进活性，和4）2.3kb mRNA的5'区具有ISRE和具有IFN-γ应答性增强活性的X-box。我们已经检测了调节蛋白的存在，在人肺成纤维细胞（HEL）的细胞核或细胞质提取物中发现了2.3kb IDO mRNA转录的增强元件，IFN-γ对IDO的诱导作用最强。然而，我们尚未在细胞核提取物中检测到此类因子。另一方面，Gupta等[J Interferon Res.15：517-526（1995）]报道了STAT 1和IRF-1都参与IDO mRNA的转录，为了证实这一点，正在对STAT 1和IRF-1缺陷小鼠中IFN-γ诱导IDO的作用进行分析。

The purpose of this study is to characterize the transcriptional factors involved in the IFN-gamma-mediated induction of indoleamine 2,3-dioxygenase (IDO), a tryptophan degrading enzyme. Until 1994, we have demonstrated that two IDO mRNAs, 1.7kb and 2.3kb, whch differ in size of 5' franking region are induced by IFN-gamma in all human cultured cell lines examined. Kinetics of both mRNA induction and analyzes of the 5' control region of IDO gene expression have shown that 1) induction of both mRNAs are blocked by inhibitors for protein synthesis, indicating the need for a de novo synthesis of protein factor (s), 2) the protein synthesis occurs within 3 h after the addition of IFN-gamma, 3) the 5' region of 1.7kb mRNA that contains IRF-1 element, ISRE element, a Y-box, and a X-box but has no IFN-gamma-responsive promoting activity for transcription of IDO mRNA,and 4) the 5' region of 2.3kb mRNA has an ISRE and a X-box with the IFN-gamma responsive enhancing activity.In 1995, we have examined the presence of regulatory protein (s) for the enhance element for transcription of 2.3kb IDO mRNA in nuclear or cytoplasmic extract of human lung fibroblasts (HEL), which exhibited the highest induction of IDO by the addition of IFN-gamma. However, we have not yet detect such factor (s) in the nuclear extract. On the other hand, Gupta et al [J Interferon Res.15 : 517-526 (1995)] have reported that both STAT1 and IRF-1 are involved in the transcription of IDO mRNA.To confirm this, analysis of IDO induction by IFN-gamma in STAT1 and IRF-1 deficient mice is in progress.