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首页> 外文期刊>Molecular and Cellular Biology >Yeast RNA Polymerase I Enhancer Is Dispensable for Transcription of the Chromosomal rRNA Gene and Cell Growth, and Its Apparent Transcription Enhancement from Ectopic Promoters Requires Fob1 Protein
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Yeast RNA Polymerase I Enhancer Is Dispensable for Transcription of the Chromosomal rRNA Gene and Cell Growth, and Its Apparent Transcription Enhancement from Ectopic Promoters Requires Fob1 Protein

机译：酵母RNA聚合酶I增强剂可用于染色体rRNA基因的转录和细胞生长，其从异位启动子的明显转录增强需要Fob1蛋白

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At the end of the 35S rRNA gene within ribosomal DNA (rDNA) repeats in Saccharomyces cerevisiae lies an enhancer that has been shown to greatly stimulate rDNA transcription in ectopic reporter systems. We found, however, that the enhancer is not necessary for normal levels of rRNA synthesis from chromosomal rDNA or for cell growth. Yeast strains which have the entire enhancer from rDNA deleted did not show any defects in growth or rRNA synthesis. We found that the stimulatory activity of the enhancer for ectopic reporters is not observed in cells with disrupted nucleolar structures, suggesting that reporter genes are in general poorly accessible to RNA polymerase I (Pol I) machinery in the nucleolus and that the enhancer improves accessibility. We also found that a fob1 mutation abolishes transcription from the enhancer-dependent rDNA promoter integrated at the HIS4 locus without any effect on transcription from chromosomal rDNA. FOB1 is required for recombination hot spot (HOT1) activity, which also requires the enhancer region, and for recombination within rDNA repeats. We suggest that Fob1 protein stimulates interactions between rDNA repeats through the enhancer region, thus helping ectopic rDNA promoters to recruit the Pol I machinery normally present in the nucleolus.
机译：在酿酒酵母中，核糖体DNA（rDNA）内35S rRNA基因重复序列的末端是一种增强子，该增强子已显示出可极大地刺激异位报道系统中的rDNA转录。但是，我们发现增强子对于从染色体rDNA合成rRNA的正常水平或细胞生长不是必需的。从rDNA缺失了完整增强子的酵母菌株在生长或rRNA合成中没有显示任何缺陷。我们发现，在核仁结构被破坏的细胞中未观察到增强子对异位报道分子的刺激活性，这表明报告子基因通常对核仁中的RNA聚合酶I（Pol I）机制的访问性较差，并且增强子提高了可访问性。我们还发现， fob1 突变消除了整合在 HIS4 基因座上的依赖增强子的rDNA启动子的转录，而对来自染色体rDNA的转录没有任何影响。 FOB1 是重组热点（ HOT1 ）活动所必需的，这也需要增强子区域，并且需要在rDNA重复序列中进行重组。我们建议，Fob1蛋白通过增强子区域刺激rDNA重复序列之间的相互作用，从而帮助异位rDNA启动子募集通常存在于核仁中的Pol I机制。

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