Morgridge Institute for Research, Madison, Wisconsin, United States of America ; Institute for Molecular Virology, University of Wisconsin, Madison, Wisconsin, United States of America ; McArdle Laboratory for Cancer Research, University of Wisconsin, Madison, Wisconsin, United States of America.
PLoS Pathog. 2013 Oct;9(10):e1003712. doi: 10.1371/journal.ppat.1003712. Epub 2013 Oct 24.
Transcription from the HIV-1 LTR promoter efficiently initiates but rapidly terminates because of a non-processive form of RNA polymerase II. This premature termination is overcome by assembly of an HIV-1 TAT/P-TEFb complex at the transactivation response region (TAR), a structured RNA element encoded by the first 59 nt of HIV-1 mRNA. Here we have identified a conserved DNA-binding element for the cellular transcription factor, ZASC1, in the HIV-1 core promoter immediately upstream of TAR. We show that ZASC1 interacts with TAT and P-TEFb, co-operating with TAT to regulate HIV-1 gene expression, and promoting HIV-1 transcriptional elongation. The importance of ZASC1 to HIV-1 transcription elongation was confirmed through mutagenesis of the ZASC1 binding sites in the LTR promoter, shRNAs targeting ZASC1 and expression of dominant negative ZASC1. Chromatin immunoprecipitation analysis revealed that ZASC1 recruits Tat and P-TEFb to the HIV-1 core promoter in a TAR-independent manner. Thus, we have identified ZASC1 as novel regulator of HIV-1 gene expression that functions through the DNA-dependent, RNA-independent recruitment of TAT/P-TEFb to the HIV-1 promoter.
HIV-1 LTR 启动子的转录有效地起始，但由于 RNA 聚合酶 II 的非连续形式而迅速终止。这种过早终止是通过 HIV-1 TAT/P-TEFb 复合物在反式激活反应区（TAR）的组装来克服的，TAR 是 HIV-1 mRNA 的前 59 个核苷酸编码的结构 RNA 元件。在这里，我们在 TAR 上游的 HIV-1 核心启动子中鉴定了细胞转录因子 ZASC1 的保守 DNA 结合元件。我们表明，ZASC1 与 TAT 和 P-TEFb 相互作用，与 TAT 合作调节 HIV-1 基因表达，并促进 HIV-1 转录延伸。通过 LTR 启动子中 ZASC1 结合位点的突变、针对 ZASC1 的 shRNA 和显性负 ZASC1 的表达，证实了 ZASC1 对 HIV-1 转录延伸的重要性。染色质免疫沉淀分析表明，ZASC1 以 TAR 独立的方式将 Tat 和 P-TEFb 募集到 HIV-1 核心启动子。因此，我们已经确定 ZASC1 是 HIV-1 基因表达的新型调节剂，它通过 DNA 依赖性、RNA 非依赖性方式将 TAT/P-TEFb 募集到 HIV-1 启动子。
