Marriott S J, Boros I, Duvall J F, Brady J N
Laboratory of Molecular Virology, National Cancer Institute, Bethesda, Maryland 20892.
Mol Cell Biol. 1989 Oct;9(10):4152-60. doi: 10.1128/mcb.9.10.4152-4160.1989.
Several laboratories have demonstrated that tandem copies of the human T-cell leukemia virus type I 21-base-pair (bp) repeat cloned upstream of either a homologous or heterologous promoter increase transcription in the presence of tax1 protein. In this report, we provide evidence for a second tax1-responsive sequence in the viral long terminal repeat. Analysis of human T-cell leukemia virus type I promoter deletion mutants and plasmids containing cloned oligonucleotide motifs demonstrated that this 47-bp sequence, located between -117 and -163, confers responsiveness to tax1. We further demonstrated that proteins present in HeLa nuclear extracts bind specifically to this tax1-responsive sequence. Mutants that affected in vivo activity also decreased in vitro binding. Using an in vitro binding assay, we demonstrated that tax1 interacts indirectly with the 47-bp sequence, most likely through protein-protein interaction. Thus, while tax1 does not bind directly to DNA to enhance transcription, it may influence sequence-specific responses by interacting with the primary DNA-protein complex.
几个实验室已证明，克隆到同源或异源启动子上游的人I型T细胞白血病病毒21碱基对（bp）重复序列的串联拷贝，在存在tax1蛋白的情况下会增加转录。在本报告中，我们提供了病毒长末端重复序列中第二个tax1反应序列的证据。对人I型T细胞白血病病毒启动子缺失突变体和含有克隆寡核苷酸基序的质粒的分析表明，这个位于-117至-163之间的47bp序列赋予了对tax1的反应性。我们进一步证明，HeLa细胞核提取物中的蛋白质与这个tax1反应序列特异性结合。影响体内活性的突变体在体外结合也减少。使用体外结合试验，我们证明tax1与47bp序列间接相互作用，最有可能是通过蛋白质-蛋白质相互作用。因此，虽然tax1不直接与DNA结合以增强转录，但它可能通过与初级DNA-蛋白质复合物相互作用来影响序列特异性反应。
