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RNase MRP is required for entry of 35S precursor rRNA into the canonical processing pathway

机译：RNase MRP是35S前体rRNA进入规范加工路径的必需条件

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摘要

RNase MRP is a nucleolar RNA–protein enzyme that participates in the processing of rRNA during ribosome biogenesis. Previous experiments suggested that RNase MRP makes a nonessential cleavage in the first internal transcribed spacer. Here we report experiments with new temperature-sensitive RNase MRP mutants in Saccharomyces cerevisiae that show that the abundance of all early intermediates in the processing pathway is severely reduced upon inactivation of RNase MRP. Transcription of rRNA continues unabated as determined by RNA polymerase run-on transcription, but the precursor rRNA transcript does not accumulate, and appears to be unstable. Taken together, these observations suggest that inactivation of RNase MRP blocks cleavage at sites A0, A1, A2, and A3, which in turn, prevents precursor rRNA from entering the canonical processing pathway (35S > 20S + 27S > 18S + 25S + 5.8S rRNA). Nevertheless, at least some cleavage at the processing site in the second internal transcribed spacer takes place to form an unusual 24S intermediate, suggesting that cleavage at C2 is not blocked. Furthermore, the long form of 5.8S rRNA is made in the absence of RNase MRP activity, but only in the presence of Xrn1p (exonuclease 1), an enzyme not required for the canonical pathway. We conclude that RNase MRP is a key enzyme for initiating the canonical processing of precursor rRNA transcripts, but alternative pathway(s) might provide a backup for production of small amounts of rRNA.
机译：RNase MRP是一种核仁RNA蛋白质酶，在核糖体生物发生过程中参与rRNA的加工。先前的实验表明，RNase MRP在第一个内部转录的间隔区进行了非必需的切割。在这里，我们报告了在酿酒酵母中使用新的温度敏感性RNase MRP突变体进行的实验，该实验表明，在RNase MRP失活后，加工途径中所有早期中间体的丰度都会大大降低。根据RNA聚合酶连续转录的确定，rRNA的转录持续进行，但前体rRNA转录物不会积累，并且似乎不稳定。综上所述，这些观察结果表明，RNase MRP的失活阻止了位点A0，A1，A2和A3的切割，从而阻止了前体rRNA进入规范加工路径（35S> 20S + 27S> 18S + 25S + 5.8S rRNA）。然而，在第二内部转录间隔区中的加工位点发生至少一些切割，以形成不寻常的24S中间体，这表明在C2的切割没有被阻断。此外，在不存在RNase MRP活性的情况下，仅在存在Xrn1p（核酸外切酶1）（标准途径不需要的酶）的情况下，才生成5.8S rRNA的长型形式。我们得出结论，RNase MRP是启动前体rRNA转录本规范处理的关键酶，但替代途径可能为少量rRNA的产生提供后备。

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  • 来源
    《RNA》 |2009年第7期|1407-1416|共10页
  • 作者

    Lasse Lindahl; Ananth Bommankanti; Xing Li; Lauren Hayden; Adrienne Jones; Miriam Khan; Tolulope Oni; Janice M. Zengel;

  • 作者单位

    Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA;

    Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA;

    Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA;

    Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA;

    Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA;

    Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA;

    Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA;

    Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA;

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  • 正文语种 eng
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  • 关键词

    rRNA processing; XRN1; exonuclease 1; rRNA turnover;

    机译：rRNA加工;XRN1;核酸外切酶1;rRNA转换;

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