Henderson A J, Zou X, Calame K L
Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
J Virol. 1995 Sep;69(9):5337-44. doi: 10.1128/JVI.69.9.5337-5344.1995.
Three binding sites for C/EBP proteins are found in the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) (V. M. Tesmer, A. Rajadhyaksha, J. Babin, and M. Bina, Proc. Natl. Acad. Sci. USA 90:7298-7302, 1993). We have determined the functional role of C/EBP proteins and C/EBP sites in regulating transcription from the HIV-1 LTR in monocytes/macrophages. Inhibition of endogenous C/EBP proteins, using either an excess of C/EBP binding sites or a trans-dominant negative inhibitor, demonstrated that C/EBP proteins are required for basal and activated levels of HIV-1 LTR transcription in the promonocytic cell line U937. Northern (RNA) blots and binding assays showed that NF-IL6 is the only known C/EBP family member which is increased when U937 cells are activated. Mutational analyses of the HIV-1 LTR showed that one C/EBP site is required for normal LTR transcription both before and after cellular activation and that the two 3' C/EBP sites are functionally equivalent. However, transcription from crippled HIV-1 LTRs lacking C/EBP sites can still be induced following activation of U937 cells. Several models are suggested for how elevated NF-IL6 may participate in an autostimulatory loop involving HIV infection, macrophage activation, cytokine expression, and HIV replication.
在人类免疫缺陷病毒1型（HIV-1）的长末端重复序列（LTR）中发现了3个C/EBP蛋白结合位点（V.M.特斯默、A.拉贾德雅克沙、J.巴宾和M.比纳，《美国国家科学院院刊》90:7298 - 7302，1993年）。我们已经确定了C/EBP蛋白和C/EBP位点在调节单核细胞/巨噬细胞中HIV-1 LTR转录方面的功能作用。使用过量的C/EBP结合位点或反式显性负抑制剂抑制内源性C/EBP蛋白，结果表明在原单核细胞系U937中，C/EBP蛋白是HIV-1 LTR基础转录水平和激活转录水平所必需的。Northern（RNA）印迹和结合试验表明，NF-IL6是唯一已知的在U937细胞被激活时表达增加的C/EBP家族成员。对HIV-1 LTR的突变分析表明，一个C/EBP位点在细胞激活前后对于正常的LTR转录都是必需的，并且两个3'端的C/EBP位点在功能上是等效的。然而，在U937细胞激活后，缺乏C/EBP位点的缺陷型HIV-1 LTR的转录仍可被诱导。针对NF-IL6升高可能如何参与涉及HIV感染、巨噬细胞激活、细胞因子表达和HIV复制的自刺激循环，提出了几种模型。
