PDF(Pubmed)
Abstract：
HIV-1 provirus expression is controlled by signaling pathways that are responsive to T cell receptor engagement, including those involving Ras and downstream protein kinases. The induction of transcription from the HIV-1 LTR in response to Ras signaling requires binding of the Ras-responsive element binding factor (RBF-2) to conserved cis elements flanking the enhancer region, designated RBE3 and RBE1. RBF-2 is composed minimally of the USF1, USF2, and TFII-I transcription factors. We recently determined that TFII-I regulates transcriptional elongation from the LTR through recruitment of the co-activator TRIM24. However, the function of USF1 and USF2 for this effect are uncharacterized. Here, we find that genetic deletion of USF2 but not USF1 in T cells inhibits HIV-1 expression. The loss of USF2 caused a reduction in expression of the USF1 protein, an effect that was not associated with decreased USF1 mRNA abundance. USF1 and USF2 were previously shown to exist predominately as heterodimers and to cooperatively regulate target genes. To examine cooperativity between these factors, we performed RNA-seq analysis of T cell lines bearing knockouts of the genes encoding these factors. In untreated cells, we found limited evidence of coordinated global gene regulation between USF1 and USF2. In contrast, we observed a high degree of genome-wide cooperative regulation of RNA expression between these factors in cells stimulated with the combination of PMA and ionomycin. In particular, we found that the deletion of USF1 or USF2 restricted T cell activation response. These observations indicate that USF2, but not USF1, is crucial for HIV-1 expression, while the combined function of these factors is required for a robust T cell inflammatory response.
摘要：
HIV-1前病毒表达受对T细胞受体参与有反应的信号通路控制，包括涉及Ras和下游蛋白激酶的那些。响应于Ras信号传导而从HIV-1LTR诱导转录需要Ras响应元件结合因子（RBF-2）与增强子区侧翼的保守顺式元件结合，指定为RBE3和RBE1。RBF-2最低限度地由USF1、USF2和TFII-I转录因子组成。我们最近确定TFII-I通过招募共激活因子TRIM24来调节LTR的转录延伸。然而,USF1和USF2对该效应的功能是未表征的。这里,我们发现T细胞中USF2而非USF1的基因缺失抑制了HIV-1的表达。USF2的丢失导致USF1蛋白表达的减少，与USF1mRNA丰度降低无关的效应.先前显示USF1和USF2主要作为异二聚体存在并协同调节靶基因。为了检查这些因素之间的协同性，我们对带有编码这些因子的基因敲除的T细胞系进行了RNA-seq分析.在未经处理的细胞中，我们发现USF1和USF2之间的整体基因调控协调的证据有限.相比之下,在PMA和离子霉素联合刺激的细胞中,我们观察到这些因子之间RNA表达的高度全基因组协同调控.特别是,我们发现USF1或USF2的缺失限制了T细胞的活化反应。这些观察结果表明，USF2，而不是USF1，对HIV-1表达至关重要。而这些因素的联合功能是强大的T细胞炎症反应所必需的。
