Abstract：
gp91(phox) is a subunit of the phagocyte respiratory burst oxidase catalytic unit. Transcription of CYBB, the gene encoding gp91(phox), is restricted to terminally differentiated phagocytic cells. An element in the proximal CYBB promoter binds a protein complex, referred to as hematopoiesis-associated factor (HAF1), that is necessary for interferon-gamma (IFNgamma)-induced gp91(phox) expression. In these investigations, we determined that HAF1 was a multiprotein complex, cross-immunoreactive with the transcription factors PU.1, interferon regulatory factor 1 (IRF-1), and interferon consensus sequence-binding protein (ICSBP). In electrophoretic mobility shift assay, the HAF1 complex was reconstituted by either in vitro translated PU.1 with IRF-1 or PU.1 with ICSBP, but not by IRF-1 with ICSBP. HAF1a, a slower mobility complex with the same binding site specificity as HAF1, was also investigated. Similar to the HAF1 complex, the HAF1a complex was cross-immunoreactive with PU. 1, IRF-1, and ICSBP. Unlike the HAF1 complex, reconstitution of the HAF1a complex required in vitro translated PU.1 with both IRF-1 and ICSBP. An artificial promoter construct containing the HAF1/HAF1a binding site was modestly activated in the myelomonocytic cell line U937 by co-transfection either with PU.1 and IRF-1 or with PU.1 and ICSBP, but it was strongly activated by co-transfection with PU.1, IRF-1, and ICSBP. This activation required serine 148-phosphorylated PU.1. These studies describe a novel mechanism for PU.1 transcriptional activation via interaction with both IRF-1 and ICSBP, a target gene for the interaction of IRF-1 with ICSBP, and a novel activation function for ICSBP as a component of a multiprotein complex.
摘要：
gp91（phox）是吞噬细胞呼吸爆发氧化酶催化单元的一个亚基。CYBB的转录,编码gp91（phox）的基因，仅限于终末分化的吞噬细胞。近端CYBB启动子中的一个元件与蛋白质复合物结合，称为造血相关因子（HAF1），这是干扰素-γ(IFNγ)诱导的gp91(phox)表达所必需的。在这些调查中,我们确定HAF1是多蛋白复合物，与转录因子PU.1，干扰素调节因子1（IRF-1），和干扰素共有序列结合蛋白(ICSBP)。在电泳迁移率变化分析中，HAF1复合物通过体外翻译PU.1与IRF-1或PU.1与ICSBP重建，但不是由IRF-1与ICSBP。HAF1a,还研究了具有与HAF1相同的结合位点特异性的较慢的迁移率复合物。类似于HAF1复合体，HAF1a复合物与PU交叉免疫反应。1、IRF-1和ICSBP。与HAF1复合体不同，HAF1a复合物的重建需要用IRF-1和ICSBP在体外翻译PU.1。通过与PU.1和IRF-1或PU.1和ICSBP共转染，在骨髓单核细胞系U937中适度激活了含有HAF1/HAF1a结合位点的人工启动子构建体，但通过与PU.1，IRF-1和ICSBP共转染而被强烈激活。这种激活需要丝氨酸148磷酸化PU1。这些研究描述了通过与IRF-1和ICSBP相互作用进行PU.1转录激活的新机制，IRF-1与ICSBP相互作用的靶基因，以及ICSBP作为多蛋白复合物成分的新型激活功能。
