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首页> 外文期刊>Molecular and Cellular Biology >Transcription of spacer sequences flanking the rat 45S ribosomal DNA gene.
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Transcription of spacer sequences flanking the rat 45S ribosomal DNA gene.

机译：大鼠45S核糖体DNA基因两侧的间隔区序列的转录。

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摘要

The transcriptional activity of spacer sequences flanking the rat 45S ribosomal DNA (rDNA) gene were studied. Nascent RNA labeled in in vitro nuclear run-on reactions hybridized with both 5' and 3' spacer regions. The highest level of hybridization was seen with an rDNA fragment containing tandem repeats of a 130-base-pair sequence upstream of the 45S rRNA initiation site. Synthesis of RNA transcripts homologous to this internally repetitious spacer region was insensitive to high levels of alpha-amanitin, suggesting that it is mediated by RNA polymerase I. Analysis of steady-state RNA showed that these transcripts were present at extremely low levels in vivo relative to precursor rRNA transcripts. In contrast, precursor and spacer run-on RNAs were synthesized at similar levels. This suggests that spacer transcripts are highly unstable in vivo; therefore, it may be the process of transcription rather than the presence of spacer transcripts that is functionally important. Transcription in this upstream rDNA region may be involved in regulation of 45S rRNA synthesis in rodents, as has been suggested previously for frog rRNA. In addition, the presence of transcriptional activity in other regions of the spacer suggests that some polymerase I molecules may transcribe through the spacer from one 45S gene to the next on rodent rDNA.
机译：研究了大鼠45S核糖体DNA（rDNA）基因两侧的间隔序列的转录活性。在体外核反应中标记的新生RNA与5'和3'间隔区杂交。杂交的最高水平是在45S rRNA起始位点上游包含130个碱基对序列的串联重复的rDNA片段。与该内部重复间隔区同源的RNA转录物的合成对高水平的α-amanitin不敏感，表明它是由RNA聚合酶I介导的。稳态RNA的分析表明，这些转录物在体内的相对水平极低。前体rRNA转录物。相反，前体和间隔区连续RNA的合成水平相似。这表明间隔转录本在体内高度不稳定。因此，在功能上很重要的可能是转录过程而不是间隔转录本的存在。上游rDNA区域中的转录可能参与了啮齿类动物45S rRNA合成的调控，如先前关于蛙rRNA的建议。另外，在间隔区的其他区域中存在转录活性，这表明某些聚合酶I分子可以通过间隔区从啮齿类rDNA上的一个45S基因转录到另一个。

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