Transcriptional activation of the integrated chromatin-associated human immunodeficiency virus type 1 promoter
Transcriptional activation of the integrated chromatin-associated human immunodeficiency virus type 1 promoter
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DOI：
10.1128/mcb.18.5.2535
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发表时间：
1998-05-01
影响因子：
5.3
通讯作者：
Martin, MA
中科院分区：
文献类型：
--
作者：
El Kharroubi, A;Piras, G;Martin, MA
人类免疫缺陷病毒 1 型 (HIV-1) 基因表达的调节涉及细胞转录因子、染色质相关前病毒 DNA 和病毒编码的反式激活蛋白 Tat 之间复杂的相互作用。在这里，我们表明，即使在没有可检测到的基础启动子活性的情况下，Tat 也会反式激活整合的 HIV-1 长末端重复序列 (LTR)，并且这种转录激活伴随着转录起始位点下游的染色质重塑，这一点通过限制性内切酶的可及性增加来监测。然而，由于缺乏 Sp1 和 NF-kappa B 位点的整合启动子，Tat 无法激活转录或诱导染色质结构的变化，即使它与 TATA 盒上游的 HIV-1 核心启动子相连。仅当 Sp1 或 NF-kappa B 与启动子结合时才观察到 Tat 反应，这意味着 Tat 在形成特定转录起始复合物后发挥作用。与 Tat 不同，NF-kappa B 无法刺激整合的转录沉默 HIV-1 启动子。组蛋白乙酰化使失活的 HIV-1 LTR 对 NF-kappa B 产生反应，表明在 NF-kappa B 转录激活之前必须重塑抑制性染色质结构。总之，这些结果表明 Sp1 和 NF-kappa B 是在整合病毒启动子上组装转录复合物所必需的，该启动子表现出连续的基础活性，所有这些都完全响应 达。
The regulation of human immunodeficiency virus type 1 (HIV-1) gene expression involves a complex interplay between cellular transcription factors, chromatin-associated proviral DNA, and the virus-encoded transactivator protein, Tat. Here we show that Tat transactivates the integrated HIV-1 long terminal repeat (LTR), even in the absence of detectable basal promoter activity and this transcriptional activation is accompanied by chromatin remodelling downstream of the transcription initiation site, as monitored by increased accessibility to restriction endonucleases. However, with an integrated promoter lacking both Sp1 and NF-kappa B sites, Tat was unable to either activate transcription or induce changes in chromatin structure even when it was tethered to the HIV-1 core promoter upstream of the TATA box. Tat responsiveness was observed only when Sp1 or NF-kappa B was bound to the promoter, implying that Tat functions subsequent to the formation of a specific transcription initiation complex. Unlike Tat, NF-kappa B failed to stimulate the integrated transcriptionally silent HIV-1 promoter. Histone acetylation renders the inactive HIV-1 LTR responsive to NF-kappa B, indicating that a suppressive chromatin structure must be remodelled prior to transcriptional activation by NF-kappa B. Taken together, these results suggest that Sp1 and NF-kappa B are required for the assembly of transcriptional complexes on the integrated viral promoter exhibiting a continuum of basal activities, all of which are fully responsive to Tat.