Kishimoto T, Nagamine M, Sasaki T, Takakusa N, Miwa T, Kominami R, Muramatsu M
Nucleic Acids Res. 1985 May 24;13(10):3515-32. doi: 10.1093/nar/13.10.3515.
Point mutations are introduced into a mouse rDNA fragment containing the promoter region by a sodium bisulfite method and the mutants are tested for the ability of accurate transcription initiation in vitro. The results indicate that the change, G to A, at -7 completely eliminates the promoter activity, and those at -16 and at -25 decrease it to about 10% and 50%, respectively. On the other hand, the substitutions at +9, +4, -2, -9 and -39 do not alter the template activity significantly. It is concluded that there are limited but distinct nucleotides that are essential for the transcription initiation of this gene. This sort of absolute requirement for single specific bases is not reported in protein coding genes transcribed by RNA polymerase II. We propose that these rigid recognition signals which we have found are the molecular basis for the strong species-dependency of the transcription machinery of RNA polymerase I system. A model is presented in which a transcription factor interacts with the rDNA promoter from one side of the DNA double-helix with essential contacts at these bases.
通过亚硫酸氢钠法将点突变引入含有启动子区域的小鼠rDNA片段中，并在体外测试这些突变体的准确转录起始能力。结果表明，-7位的G到A的变化完全消除了启动子活性，-16位和-25位的变化分别将其降低到约10%和50%。另一方面，+9、+4、-2、-9和-39位的取代对模板活性没有显著影响。得出的结论是，对于该基因的转录起始，存在有限但不同的核苷酸是必不可少的。这种对单个特定碱基的绝对要求在RNA聚合酶II转录的蛋白质编码基因中未见报道。我们提出，我们发现的这些严格的识别信号是RNA聚合酶I系统转录机制强烈物种依赖性的分子基础。提出了一个模型，其中转录因子从DNA双螺旋的一侧与rDNA启动子相互作用，并在这些碱基处进行关键接触。
