Hanas J S, Smith J F
Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
Nucleic Acids Res. 1990 May 25;18(10):2923-8. doi: 10.1093/nar/18.10.2923.
Xenopus transcription factor IIIA (TFIIIA) regulates 5S ribosomal RNA gene transcription in a positive manner by binding to the internal control region (ICR) of the 5S RNA gene. The present study reports the identification of a TFIIIA binding site on the 5' flanking region of the Xenopus laevis gene that codes for the synthesis of this transcription factor. This TFIIIA binding site (deduced from TFIIIA-dependent alterations in DNase I protection patterns) extends on the 5' flanking region from about nucleotide -326 to -264 on the non-coding strand and from -331 to -271 on the coding strand. The affinity of TFIIIA for the 5' flanking region of its own gene is less than that for the 5S RNA gene but within the same order of magnitude. A sequence similarity between this newly identified binding site and the 5S gene ICR is the presence of purine-rich tracts. EDTA chelation of TFIIIA inhibits binding to this 5' flanking element indicating, as with the 5S RNA gene, zinc is required for DNA binding specificity. When TFIIIA is bound to 5S RNA in the 7S particle, the protein does not bind to this 5' flanking region, an observation similar to that observed with binding to the 5S RNA gene. These results indicate TFIIIA is using similar nucleic acid binding domain(s) for interaction with the 5S gene, 5S RNA, and the 5' flanking region of its own gene. This upstream DNA region to which TFIIIA binds has been previously shown to contain a negative and a positive regulatory element for transcription of the TFIIIA gene (Scotto, K.W., Kaulen, H., and Roeder, R.G., 1989, Genes & Develop. 3, 651-662). The present results indicate TFIIIA binds to the negative control element located at -306 to -289 and possibly interacts/interferes with another transcription factor which binds to the positive control element extending from -271 to -253.
非洲爪蟾转录因子IIIA（TFIIIA）通过与5S核糖体RNA基因的内部控制区（ICR）结合，以正向方式调节5S核糖体RNA基因的转录。本研究报告了在非洲爪蟾基因5'侧翼区域鉴定出一个TFIIIA结合位点，该基因编码这种转录因子的合成。这个TFIIIA结合位点（从DNase I保护模式中依赖TFIIIA的改变推断得出）在5'侧翼区域，非编码链上从约核苷酸-326延伸至-264，编码链上从-331延伸至-271。TFIIIA对其自身基因5'侧翼区域的亲和力低于对5S RNA基因的亲和力，但在同一数量级内。这个新鉴定的结合位点与5S基因ICR之间的序列相似性在于富含嘌呤的区域。TFIIIA的EDTA螯合作用会抑制其与这个5'侧翼元件的结合，这表明与5S RNA基因一样，DNA结合特异性需要锌。当TFIIIA在7S颗粒中与5S RNA结合时，该蛋白不会与这个5'侧翼区域结合，这一观察结果与结合到5S RNA基因时观察到的相似。这些结果表明TFIIIA正在使用相似的核酸结合结构域与5S基因、5S RNA及其自身基因的5'侧翼区域相互作用。先前已表明TFIIIA结合的这个上游DNA区域包含TFIIIA基因转录的一个负调控元件和一个正调控元件（斯科托，K.W.，考伦，H.，和罗德，R.G.，1989，《基因与发育》3，651 - 662）。目前的结果表明TFIIIA与位于-306至-289的负调控元件结合，并可能与另一个结合从-271延伸至-253的正调控元件的转录因子相互作用/干扰。
