Yamashita I, Katamine S, Moriuchi R, Nakamura Y, Miyamoto T, Eguchi K, Nagataki S
First Department of Internal Medicine, Nagasaki University School of Medicine, Japan.
Blood. 1994 Sep 1;84(5):1573-8.
Interleukin-6 (IL-6) is a multifunctional cytokine that regulates both humoral and cellular immune responses. Accumulating evidence suggests that the infection of T cells and other cell types with human T-lymphotropic virus type 1 (HTLV-1) results in the constitutive expression of IL-6. However, the underlying molecular mechanisms are little understood. When a reporter plasmid, pIL6-CAT-E3, in which the human IL-6 enhancer/promoter region from -630 to +14 was linked to the bacterial chloramphenicol acetyltransferase (CAT) gene, was transfected, HTLV-1-infected but not -uninfected T-cell lines activated the IL-6 promoter. This indicated the presence of a factor transactivating the IL-6 gene in the infected cells. To evaluate the involvement of the HTLV-1-encoded transacting factor (Tax) in this transactivation, we examined the effect of transient cotransfection with the Tax-expression plasmid, pMAX-Neo, on the transcription from the IL-6 promoter by use of COS1 cells. The cotransfected COS1 has about six-times greater the CAT activity than that transfected with pIL6-CAT-E3 alone. The analysis of a series of deletions of the IL-6 promoter suggested that the region (-105/-47) containing a NF kappa B site was crucial for the Tax responsiveness. We further examined the effect of Tax on endogenous IL-6 gene expression using the Jurkat clone, JPX-9, stably transfected with pMAX-Neo. JPX-9 accumulated steady state transcripts of the endogenous IL-6 gene in response to the induction of Tax expression. Our findings indicate an important role of the Tax protein in the expression of IL-6 in cells infected with HTLV-1.
白细胞介素-6（IL-6）是一种多功能细胞因子，可调节体液免疫和细胞免疫反应。越来越多的证据表明，人类1型嗜T淋巴细胞病毒（HTLV-1）感染T细胞和其他细胞类型会导致IL-6的组成性表达。然而，其潜在的分子机制尚不清楚。当将报告质粒pIL6-CAT-E3（其中人类IL-6增强子/启动子区域从-630至+14与细菌氯霉素乙酰转移酶（CAT）基因相连）转染时，HTLV-1感染而非未感染的T细胞系激活了IL-6启动子。这表明在感染细胞中存在一种反式激活IL-6基因的因子。为了评估HTLV-1编码的反式作用因子（Tax）在这种反式激活中的作用，我们通过使用COS1细胞检测了与Tax表达质粒pMAX-Neo瞬时共转染对IL-6启动子转录的影响。共转染的COS1细胞的CAT活性比单独转染pIL6-CAT-E3的细胞高约六倍。对IL-6启动子一系列缺失的分析表明，包含NFκB位点的区域（-105 / -47）对Tax反应性至关重要。我们进一步使用稳定转染pMAX-Neo的Jurkat克隆JPX-9检测了Tax对内源性IL-6基因表达的影响。JPX-9在Tax表达诱导下积累了内源性IL-6基因的稳态转录本。我们的研究结果表明Tax蛋白在HTLV-1感染细胞中IL-6的表达中起重要作用。
