A-U3 SNORNP PROTEIN WITH HOMOLOGY TO SPLICING FACTOR PRP4 AND G-BETA-DOMAINS IS REQUIRED FOR RIBOSOMAL-RNA PROCESSING
A-U3 SNORNP PROTEIN WITH HOMOLOGY TO SPLICING FACTOR PRP4 AND G-BETA-DOMAINS IS REQUIRED FOR RIBOSOMAL-RNA PROCESSING
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DOI：
10.1002/j.1460-2075.1993.tb05910.x
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发表时间：
1993-06-01
期刊：
影响因子：
11.4
通讯作者：
HURT, EC
中科院分区：
文献类型：
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作者：
JANSEN, R;TOLLERVEY, D;HURT, EC
酵母纤维蛋白 (NOP1) 是一种进化上保守的核仁蛋白，是核糖体生物发生的多个步骤所必需的。缺乏功能性 NOP1 基因的酵母突变体可以通过人纤维蛋白补充，但对生长温度敏感，并且前 rRNA 加工受损。为了鉴定在酵母中与人纤维蛋白功能性相互作用的成分，我们分离了该表型的外源抑制因子。通过体内互补克隆了一种显性抑制因子 sof1-56，它对人纤维蛋白具有等位基因特异性，可在 35 摄氏度下恢复生长和前 RNA 加工。 SOF1 的野生型等位基因对于细胞生长至关重要，并编码一种新型 56 kDa 蛋白质。 SOF1 在其中心结构域中包含一个重复序列，该序列也存在于三聚体 G 蛋白的 β 亚基和剪接因子 PRP4 中。 G(β) 样重复结构域中的单个氨基酸交换导致了 sof1-56 的抑制活性。间接免疫荧光显示 SOF1 位于酵母核仁内。免疫共沉淀证明了 SOF1 与 U3 小核仁 RNA 和 NOP1 的物理关联。 SOF1 的体内耗竭会导致前 rRNA 加工受损并抑制 18S rRNA 产生。因此，SOF1 是核仁 rRNA 加工机器的一个新组件。
Yeast fibrillarin (NOP1) is an evolutionarily conserved, nucleolar protein necessary for multiple steps in ribosome biogenesis. Yeast mutants lacking a functional NOP1 gene can be complemented by human fibrillarin but are temperature sensitive for growth and impaired in pre-rRNA processing. In order to identify components which interact functionally with human fibrillarin in yeast, we isolated extragenic suppressors of this phenotype. One dominant suppressor, sof1-56, which is allele-specific for human fibrillarin and restores growth and pre-RNA processing at 35-degrees-C, was cloned by in vivo complementation. The wild-type allele of SOF1 is essential for cell growth and encodes a novel 56 kDa protein. In its central domain, SOF1 contains a repeated sequence also found in beta-subunits of trimeric G-proteins and the splicing factor PRP4. A single amino acid exchange in the G(beta)-like repeat domain is responsible for the suppressing activity of sof1-56. Indirect immunofluorescence shows that SOF1 is located within the yeast nucleolus. Co-immunoprecipitation demonstrates the physical association of SOF1 with U3 small nucleolar RNA and NOP1. In vivo depletion of SOF1 leads to impaired pre-rRNA processing and inhibition of 18S rRNA production. Thus, SOF1 is a new component of the nucleolar rRNA processing machinery.