Qiu Hui, Eifert Julia, Wacheul Ludivine, Thiry Marc, Berger Adam C, Jakovljevic Jelena, Woolford John L, Corbett Anita H, Lafontaine Denis L J, Terns Rebecca M, Terns Michael P
Department of Biochemistry and Molecular Biology, University of Georgia, Davison Life Sciences Complex, Green Street, Athens, GA 30602, USA.
Mol Cell Biol. 2008 Jun;28(11):3686-99. doi: 10.1128/MCB.01115-07. Epub 2008 Mar 31.
Small nucleolar RNAs (snoRNAs) orchestrate the modification and cleavage of pre-rRNA and are essential for ribosome biogenesis. Recent data suggest that after nucleoplasmic synthesis, snoRNAs transiently localize to the Cajal body (in plant and animal cells) or the homologous nucleolar body (in budding yeast) for maturation and assembly into snoRNPs prior to accumulation in their primary functional site, the nucleolus. However, little is known about the trans-acting factors important for the intranuclear trafficking and nucleolar localization of snoRNAs. Here, we describe a large-scale genetic screen to identify proteins important for snoRNA transport in Saccharomyces cerevisiae. We performed fluorescence in situ hybridization analysis to visualize U3 snoRNA localization in a collection of temperature-sensitive yeast mutants. We have identified Nop4, Prp21, Tao3, Sec14, and Htl1 as proteins important for the proper localization of U3 snoRNA. Mutations in genes encoding these proteins lead to specific defects in the targeting or retention of the snoRNA to either the nucleolar body or the nucleolus. Additional characterization of the mutants revealed impairment in specific steps of U3 snoRNA processing, demonstrating that snoRNA maturation and trafficking are linked processes.
小核仁RNA（snoRNA）参与前体rRNA的修饰和切割，对核糖体生物合成至关重要。最近的数据表明，在核质合成后，snoRNA会短暂定位于卡哈尔体（在植物和动物细胞中）或同源核仁体（在芽殖酵母中）进行成熟，并组装成snoRNP，然后才在其主要功能位点核仁中积累。然而，对于snoRNA核内运输和核仁定位的重要反式作用因子知之甚少。在这里，我们描述了一项大规模遗传筛选，以鉴定酿酒酵母中对snoRNA运输重要的蛋白质。我们进行了荧光原位杂交分析，以观察U3 snoRNA在一组温度敏感酵母突变体中的定位。我们已鉴定出Nop4、Prp21、Tao3、Sec14和Htl1是对U3 snoRNA正确定位重要的蛋白质。编码这些蛋白质的基因突变会导致snoRNA靶向或保留到核仁体或核仁出现特定缺陷。对这些突变体的进一步表征揭示了U3 snoRNA加工特定步骤的受损，表明snoRNA成熟和运输是相互关联的过程。
