Mukerjee Ruma, Sawaya Bassel E, Khalili Kamel, Amini Shohreh
Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, Philadelphia, Pennsylvania 19122, USA.
J Cell Biochem. 2007 Apr 1;100(5):1210-6. doi: 10.1002/jcb.21109.
In human immunodeficiency virus type 1 (HIV-1) latently infected cells, NF-kappaB (NF-kappaB) plays a critical role in the transcriptional induction of the HIV-1 promoter. The trans-activating ability of NF-kappaB can be modified by another nuclear factor C/EBPbeta that can physically bind to NF-kappaB and regulate its activity. Because the HIV-1 promoter also contains a C/EBPbeta site adjacent to the NF-kappaB site, the present study examined cooperative functional in vivo interaction of the p65 subunit of NF-kappaB and C/EBPbeta, and the impact of Tat in this event. We demonstrated that ectopic expression of p65 along with Tat increases p65 binding to HIV-1 LTR, and that this increase correlates with enhanced HIV-1 promoter activity. Further, co-expression of C/EBPbeta and Tat leads to a decrease in p65 binding, which allows C/EBPbeta to bind more efficiently to the LTR. Inhibition of p65 expression by siRNA significantly decreases C/EBPbeta-binding and LTR expression. Using ChIP assay, we confirmed the existence of an interchange between p65 and C/EBPbeta and their abilities to bind to the LTR in vivo. These observations demonstrate that a delicate balance of interaction between p65, C/EBPbeta, and Tat can dictate the level of HIV-1 LTR transcription.
在1型人类免疫缺陷病毒（HIV-1）潜伏感染的细胞中，核因子κB（NF-κB）在HIV-1启动子的转录诱导中起关键作用。NF-κB的反式激活能力可被另一种核因子C/EBPβ修饰，C/EBPβ可与NF-κB物理结合并调节其活性。由于HIV-1启动子在NF-κB位点附近还含有一个C/EBPβ位点，本研究检测了NF-κB的p65亚基与C/EBPβ在体内的协同功能相互作用，以及Tat在此过程中的影响。我们证明，p65与Tat的异位表达增加了p65与HIV-1长末端重复序列（LTR）的结合，且这种增加与HIV-1启动子活性增强相关。此外，C/EBPβ与Tat的共表达导致p65结合减少，这使得C/EBPβ能更有效地与LTR结合。用小干扰RNA（siRNA）抑制p65表达可显著降低C/EBPβ结合及LTR表达。通过染色质免疫沉淀（ChIP）分析，我们证实了p65与C/EBPβ之间存在互换，以及它们在体内与LTR结合的能力。这些观察结果表明，p65、C/EBPβ和Tat之间相互作用的微妙平衡可决定HIV-1 LTR转录水平。
