Wessner R, Yao J, Wigdahl B
Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, Hershey 17033, USA.
Leukemia. 1997 Apr;11 Suppl 3:10-3.
Human T cell lymphotropic virus type I (HTLV-I) encodes the transactivator protein, Tax, which facilitates viral transcription from three 21 bp repeated elements within the U3 region of the long terminal repeat (LTR). Examination of the basal factors interacting with the 21 bp repeat elements through electrophoretic mobility shift (EMS) analyses has demonstrated the formation of DNA-protein complexes common to each of the 21 bp repeats (C1-C3) as well as three DNA-protein complexes specific to the promoter proximal (pp) repeat (U1 (U1A/U1B) and U2; 1-4). These studies have indicated that the individual repeats are not identical with respect to the cellular factors with which they interact. EMS analyses utilizing a series of mutated pp repeat elements demonstrate that the nucleotide sequence requirements for U1 (U1A/U1B) and U2 formation are separable from those required for C1-C3 formation. Competition EMS analyses utilizing Sp1 and CREB binding site oligonucleotides demonstrate that Sp family members are critical components of U1 (U1A/U1B) and U2 and that ATF/CREB family members are critical components of C1-C3. EMS supershift analyses have demonstrated that Sp1 is involved in U1A formation while Sp3 is involved in U1B and U2 formation. EMS analyses performed with nuclear extracts from Tax-expressing Jurkat cells and HTLV-I-transformed peripheral blood mononuclear cells demonstrate that Tax prevents the formation of U1 (U1A/U1B) and U2 DNA-protein complexes. Therefore, Tax appears to inhibit the interaction of Sp family members with the pp repeat. Based on these observations, it is possible that the interaction of Sp and ATF/CREB family members with the pp repeat during basal and Tax-mediated transcription may play a critical role in viral gene expression during the initial stages of virus infection or during activation of a latent infection.
人类嗜T细胞病毒I型（HTLV-I）编码反式激活蛋白Tax，该蛋白可促进病毒从长末端重复序列（LTR）U3区域内的三个21 bp重复元件进行转录。通过电泳迁移率变动（EMS）分析对与21 bp重复元件相互作用的基础因子进行检测，结果表明每个21 bp重复序列（C1-C3）都形成了DNA-蛋白质复合物，以及启动子近端（pp）重复序列特有的三种DNA-蛋白质复合物（U1（U1A/U1B）和U2；1-4）。这些研究表明，各个重复序列在与其相互作用的细胞因子方面并不相同。利用一系列突变的pp重复元件进行的EMS分析表明，U1（U1A/U1B）和U2形成所需的核苷酸序列要求与C1-C3形成所需的序列要求是可分离的。利用Sp1和CREB结合位点寡核苷酸进行的竞争EMS分析表明，Sp家族成员是U1（U1A/U1B）和U2的关键组成部分，而ATF/CREB家族成员是C1-C3的关键组成部分。EMS超迁移分析表明，Sp1参与U1A的形成，而Sp3参与U1B和U2的形成。用表达Tax的Jurkat细胞和HTLV-I转化的外周血单核细胞的核提取物进行的EMS分析表明，Tax可阻止U1（U1A/U1B）和U2 DNA-蛋白质复合物的形成。因此，Tax似乎抑制了Sp家族成员与pp重复序列的相互作用。基于这些观察结果，在基础转录和Tax介导的转录过程中，Sp和ATF/CREB家族成员与pp重复序列的相互作用可能在病毒感染初期或潜伏感染激活期间的病毒基因表达中起关键作用。
