Dunaway M, Ostrander E A
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Nature. 1993 Feb 25;361(6414):746-8. doi: 10.1038/361746a0.
Experiments correlating template topology with transcriptional activity suggest that DNA topology plays a role in eukaryotic gene expression. Linear templates transfected into cultured cells produce far fewer transcripts than do circular transcription templates, and no transcripts can be detected from linear templates injected into Xenopus oocytes. Further, when transcriptionally active circular templates in Xenopus oocytes are linearized by injection of a restriction enzyme, transcription dramatically decreases. Here we show that transcription by phage T7 RNA polymerase from a divergent promoter can partially replace the requirement for circular Xenopus ribosomal RNA transcription templates in Xenopus oocytes. Supercoiled domains can apparently be generated on short pieces of DNA having no known sequences that result in association with the nuclear architecture, suggesting that localized, transient domains of supercoiling fulfil the minimum topological needs for Xenopus rRNA transcription in vivo.
将模板拓扑结构与转录活性相关联的实验表明，DNA拓扑结构在真核基因表达中发挥作用。转染到培养细胞中的线性模板产生的转录本比环状转录模板少得多，并且从注射到非洲爪蟾卵母细胞中的线性模板中检测不到转录本。此外，当通过注射限制酶使非洲爪蟾卵母细胞中转录活性的环状模板线性化时，转录会显著降低。在这里，我们表明噬菌体T7 RNA聚合酶从一个发散启动子进行的转录可以部分替代非洲爪蟾卵母细胞中环状非洲爪蟾核糖体RNA转录模板的需求。超螺旋结构域显然可以在没有已知序列的短片段DNA上产生，这些序列会导致与核结构相关联，这表明局部的、短暂的超螺旋结构域满足了非洲爪蟾rRNA在体内转录的最低拓扑需求。
