Molecular Epigenetics Group, Department of Biochemistry and Molecular Biology, LSI, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
Viruses. 2023 Jun 28;15(7):1470. doi: 10.3390/v15071470.
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 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 but not 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 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 or 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.
HIV-1 前病毒的表达受 T 细胞受体结合所引发的信号通路调控，包括 Ras 和下游蛋白激酶信号通路。Ras 信号诱导 HIV-1 LTR 的转录需要 Ras 反应元件结合因子（RBF-2）与侧翼增强子区域的保守元件（称为 RBE3 和 RBE1）结合。RBF-2 至少由 USF1、USF2 和 TFII-I 转录因子组成。我们最近发现，TFII-I 通过募集共激活因子 TRIM24 来调节 LTR 的转录延伸。然而，对于这种效应，USF1 和 USF2 的功能尚未确定。在这里，我们发现 T 细胞中 的基因缺失而非 的基因缺失抑制了 HIV-1 的表达。USF2 的缺失导致 USF1 蛋白表达减少，这种效应与 mRNA 丰度降低无关。USF1 和 USF2 先前被证明主要以异源二聚体形式存在，并协同调节靶基因。为了研究这些因子之间的协同作用，我们对携带这些因子基因敲除的 T 细胞系进行了 RNA-seq 分析。在未处理的细胞中，我们发现 USF1 和 USF2 之间协调的全局基因调控的证据有限。相比之下，我们观察到在 PMA 和离子霉素联合刺激的细胞中，这些因子之间存在高度的全基因组协同调节 RNA 表达。特别是，我们发现 或 的缺失限制了 T 细胞激活反应。这些观察结果表明，USF2（而非 USF1）对 HIV-1 的表达至关重要，而这些因子的联合功能对于强大的 T 细胞炎症反应是必需的。
