Grimaldi G, Di Nocera P P
Nucleic Acids Res. 1986 Aug 26;14(16):6417-32. doi: 10.1093/nar/14.16.6417.
Recombinant plasmids that carry the bacterial CAT gene under the transcriptional control of the D. melanogaster rDNA promoter have been introduced by transfection into cultured Schneider II Drosophila cells and their template activity followed at the RNA and protein level. While no CAT enzyme activity is measurable 48 hrs after transfection, high levels of hybrid rRNA-CAT transcripts that originate at the authentic rRNA start site are detected by S1 mapping analysis. The interval -180/+34 of a rDNA transcriptional unit is sufficient to ensure faithful polymerase I transcription. However, the presence of a complete NTS (non transcribed spacer) region greatly enhances the transcriptional activity of exogenously added rDNA templates. Competition experiments between constructs carrying different amounts of NTS sequences indicate that spacer segments confer a transcriptional advantage efficiently attracting necessary transcription factors and/or polymerase I molecules.
携带在黑腹果蝇rDNA启动子转录控制下的细菌CAT基因的重组质粒，已通过转染导入培养的施耐德II型果蝇细胞，并在RNA和蛋白质水平上跟踪其模板活性。转染48小时后未检测到CAT酶活性，但通过S1图谱分析检测到起源于真实rRNA起始位点的高水平杂交rRNA-CAT转录本。rDNA转录单位的-180/+34区间足以确保聚合酶I的忠实转录。然而，完整的非转录间隔区（NTS）的存在极大地增强了外源添加的rDNA模板的转录活性。携带不同数量NTS序列的构建体之间的竞争实验表明，间隔区片段赋予转录优势，能有效吸引必要的转录因子和/或聚合酶I分子。
