Torchet C, Hermann-Le Denmat S
Laboratoire de Génétique Moléculaire, Ecole Normale Supérieure, CNRS UMR 8541, F-75230 (Cedex 05) Paris, France.
Mol Genet Genomics. 2002 Sep;268(1):70-80. doi: 10.1007/s00438-002-0724-z. Epub 2002 Jul 20.
We have previously described a yeast strain in which cleavage at site A2 during processing of rRNA is absent and is functionally replaced by cleavage at site A3. This strain expresses a variant of the essential RRP5 gene that results in the synthesis of two noncontiguous segments of the protein. We have used the slow-growth phenotype of this strain to screen for revertants. The gene for the small nucleolar RNA snR10 was isolated as a multicopy suppressor of this "bipartite" RRP5 allele. Suppression by snR10 efficiently rescues the slow-growth (sg) and temperature-sensitive (ts) phenotypes of the mutant strain and is specific for this small nucleolar RNA. Deletion derivatives of snR10 were constructed and tested for the ability to suppress the sg and ts phenotypes of the RRP5 mutant, as well as for complementation of the cold sensitivity of a delta snr10 strain. The results indicate that the suppression effect is more sensitive to snR10 mutations than is complementation. The high dosage of wild-type snR10 does not restore cleavage at A2, but improves the rate of pre-rRNA processing and significantly increases the level of active ribosomes in the suppressed strain. These effects probably account for the suppression of the sg and ts phenotypes of the rrp5 mutant strain.
我们之前描述过一种酵母菌株，该菌株在rRNA加工过程中不存在A2位点的切割，而是在功能上被A3位点的切割所取代。该菌株表达一种必需的RRP5基因变体，其导致合成该蛋白质的两个不连续片段。我们利用该菌株的生长缓慢表型来筛选回复突变体。小核仁RNA snR10的基因被分离出来作为这种“二分体”RRP5等位基因的多拷贝抑制子。snR10的抑制作用有效地挽救了突变菌株的生长缓慢（sg）和温度敏感（ts）表型，并且对这种小核仁RNA具有特异性。构建了snR10的缺失衍生物，并测试其抑制RRP5突变体的sg和ts表型的能力，以及对delta snr10菌株冷敏感性的互补能力。结果表明，抑制作用比互补作用对snR10突变更敏感。高剂量的野生型snR10不能恢复A2位点的切割，但提高了前体rRNA加工的速率，并显著增加了被抑制菌株中活性核糖体的水平。这些效应可能解释了rrp5突变菌株的sg和ts表型的抑制现象。
