Twenty-one base pair repeat elements influence the ability of a Gal4-Tax fusion protein to transactivate the HTLV-I long terminal repeat.
Twenty-one base pair repeat elements influence the ability of a Gal4-Tax fusion protein to transactivate the HTLV-I long terminal repeat.
复制标题
二十一个碱基对重复元件影响 Gal4-Tax 融合蛋白反式激活 HTLV-I 长末端重复序列的能力。
DOI：
10.1006/viro.1993.1408
复制
发表时间：
1993
期刊：
影响因子：
3.7
通讯作者：
Marriott,SJ
中科院分区：
文献类型：
--
作者：
Connor,LM;Oxman,MN;Brady,JN;Marriott,SJ
人t细胞白血病病毒（HTLV-I）的tax1蛋白是一个40 kda的病毒基因表达阳性反激活因子。tax1不直接与DNA结合，但通过细胞转录因子与DNA间接结合。为了进一步研究Tax1对HTLV-I转录的激活作用，我们构建了一个融合到Gal4 DNA结合域的含有Tax1的嵌合蛋白（Gal4- tax）。构建HTLV-I长末端重复序列（LTR）报告质粒，其中特定的tax1响应元件被Gal4结合位点取代。将Gal4- tax或tax1与含有Gal4结合位点的HTLV-I LTR报告基因共转染表明，Gal4序列对于Gal4- tax最大激活启动子是必要的，但不是充分的。围绕Gal4结合位点的序列对于确定Gal4- tax的激活水平很重要。Gal4- tax与含有6个Gal4结合位点但缺乏侧翼LTR序列的启动子的关联被Gal4- tax弱反激活（7倍）。相比之下，含有三个Gal4结合位点和两个21碱基对重复元件的LTR-CAT报告结构对Gal4- tax的反应要高9倍。这些结果表明，结合21个碱基对重复元件的细胞转录因子影响了tax1作为反激活子的功能。此外，这种影响并不能完全解释为这些因素在物理上引导tax1到LTR的能力。
The Tax1protein of the human T-cell leukemia virus (HTLV-I) is a 40-kDa positive transactivator of viral gene expression. Tax1does not bind directly to DNA, but associates indirectly with DNA via cellular transcription factors. To further investigate the activation of HTLV-I transcription by Tax1, a chimeric protein containing Tax1fused to the DNA binding domain of Gal4 was created (Gal4-Tax). HTLV-I long terminal repeat (LTR) reporter plasmids were constructed in which specific Tax1responsive elements were replaced with Gal4 binding sites. Cotransfection of Gal4-Tax or Tax1with HTLV-I LTR reporter constructs containing Gal4 binding sites demonstrated that Gal4 sequences were necessary but not sufficient for maximal activation of the promoter by Gal4-Tax. Sequences surrounding the Gal4 binding sites were important in determining the level of Gal4-Tax activation. Association of Gal4-Tax with promoters which contained six Gal4 binding sites, but which lacked flanking LTR sequences, were weakly transactivated by Gal4-Tax (sevenfold). In contrast, LTR-CAT reporter constructs containing three Gal4 binding sites flanked by two 21 base pair repeat elements demonstrated a ninefold greater response to Gal4-Tax. These results suggest that cellular transcription factors, which bind the 21 base pair repeat elements, influence the ability of Tax1to function as a transactivator. Furthermore, this effect is not fully explained by the ability of these factors to physically direct Tax1to the LTR.