A split binding site for TFIIIC on the Xenopus 5S gene.
A split binding site for TFIIIC on the Xenopus 5S gene.
复制标题
非洲爪蟾 5S 基因上 TFIIIC 的分裂结合位点。
作者：
K. Majowski;H. Mentzel;T. Pieler
我们之前已经证明，在构成Xenopus 5S基因启动子的两个功能域中，共同的、保守的box A元件直接参与共同转录因子IIIC的结合。在这里，我们描述了5S基因特异性启动子元件box C在转录因子结合中的作用的研究。对22种不同的单位点碱基对变化的分析表明，由于对TFIIIA的亲和力降低，在该片段的5′‐区域产生的突变会干扰转录，而在同一元件的3′‐区域引入的序列改变同样会抑制转录，但不会导致TFIIIA结合的可测量缺陷。相反，它们明显降低了对TFIIIC的亲和力。TFIIIA对盒A和盒C间距增加的5S突变体的DNA酶I保护实验表明，TFIIIA识别特定的盒A序列元件，并且该因子必须在DNA模板上正确对齐，以便与TFIIIC进行稳定的复合物形成。本文将根据这些结果对5S基因内控制区蛋白结合信号的结构和功能组织进行探讨。
We have previously shown that of the two functional domains which constitute the Xenopus 5S gene promoter the common, conserved box A element is directly involved in the binding of the common transcription factor IIIC. Here, we describe the investigation of the role of the 5S gene specific promoter element, box C, in transcription factor binding. Analysis of 22 different single site basepair changes reveals that mutations created within the 5′‐region of this segment interfere with transcription due to a reduced affinity for TFIIIA, whereas sequence alterations introduced into the 3′‐region of the same element similarly inhibit transcription, but do not result in a measurable defect in TFIIIA binding. Instead, they clearly reduce the affinity for TFIIIC. DNase I protection experiments with TFIIIA on 5S mutants which have an increased spacing of box A and box C demonstrate that TFIIIA recognizes a specific box A sequence element and that the factor has to be properly aligned on the DNA template in order to allow stable complex formation with TFIIIC to proceed. The structural and functional organization of protein binding signals on the 5S gene internal control region will be discussed in regard to these results.