Morgan G T, Roan J G, Bakken A H, Reeder R H
Nucleic Acids Res. 1984 Aug 10;12(15):6043-52. doi: 10.1093/nar/12.15.6043.
We have compared the DNA sequences of several different examples of the duplicated polymerase I promoters that are found in rDNA spacers of Xenopus laevis. Although different spacers exhibit different amounts of transcription in vivo, this does not seem to be due to DNA sequence differences between spacer promoters. We have found that several different spacer promoters when subcloned and injected into oocytes exhibit similar promoter activities when transcription is assayed by primer extension analysis. Moreover, the activity of these spacer promoters is the same as that of a co-injected gene promoter. The equivalence of spacer promoter activity and gene promoter activity was also found when rDNA plasmids containing intact spacers were injected into oocytes and transcription assayed by primer extension. This is in contrast to (1) the inactivity normally exhibited by the promoters of endogenous spacers in oocytes, (2) the relative inactivity of spacer promoters found when transcription of the same rDNA plasmids is assayed by electron microscopy.
我们比较了在非洲爪蟾核糖体DNA间隔区中发现的几个不同的重复聚合酶I启动子的DNA序列。尽管不同的间隔区在体内表现出不同程度的转录，但这似乎并非由于间隔区启动子之间的DNA序列差异所致。我们发现，当通过引物延伸分析检测转录时，几个不同的间隔区启动子亚克隆并注射到卵母细胞中时表现出相似的启动子活性。此外，这些间隔区启动子的活性与共注射的基因启动子的活性相同。当将含有完整间隔区的核糖体DNA质粒注射到卵母细胞中并通过引物延伸分析检测转录时，也发现了间隔区启动子活性和基因启动子活性的等效性。这与以下情况形成对比：(1)卵母细胞中内源性间隔区启动子通常表现出的无活性；(2)当通过电子显微镜检测相同核糖体DNA质粒的转录时发现的间隔区启动子的相对无活性。
