Wiederkehr T, Prétôt R F, Minvielle-Sebastia L
Department of Cell Biology, Biozentrum, University of Basel, Switzerland.
RNA. 1998 Nov;4(11):1357-72. doi: 10.1017/s1355838298980955.
To identify new genes involved in 3'-end formation of mRNAs in Saccharomyces cerevisiae, we carried out a screen for synthetic lethal mutants with the conditional poly(A) polymerase allele, pap1-7. Five independent temperature-sensitive mutations called Icp1 to Icp5 (for lethal with conditional pap1 allele) were isolated. Here, we describe the characterization of the essential gene LCP5 which codes for a protein with a calculated molecular mass of 40.8 kD. Unexpectedly, we found that mutations in LCP5 caused defects in pre-ribosomal RNA (pre-rRNA) processing, whereas mRNA 3'-end formation in vitro was comparable to wild-type. Early cleavage steps (denoted A0 to A2) that lead to the production of mature 18S rRNA were impaired. In vivo depletion of Lcp5p also inhibited pre-rRNA processing. As a consequence, mutant and depleted cells showed decreased levels of polysomes compared to wild-type cells. Indirect immunofluorescence indicated a predominant localization of Lcp5p in the nucleolus. In addition, antibodies directed against Lcp5p specifically immunoprecipitated the yeast U3 snoRNA snR17, suggesting that the protein is directly involved in pre-rRNA processing.
为了鉴定酿酒酵母中参与mRNA 3'末端形成的新基因,我们对与条件性多聚腺苷酸聚合酶等位基因pap1-7合成致死的突变体进行了筛选。分离出了五个独立的温度敏感突变,分别称为Icp1至Icp5(与条件性pap1等位基因致死)。在此,我们描述了必需基因LCP5的特征,该基因编码一种计算分子量为40.8 kD的蛋白质。出乎意料的是,我们发现LCP5中的突变导致核糖体前体RNA(pre-rRNA)加工缺陷,而体外mRNA 3'末端形成与野生型相当。导致成熟18S rRNA产生的早期切割步骤(标记为A0至A2)受到损害。体内Lcp5p的缺失也抑制了pre-rRNA加工。因此,与野生型细胞相比,突变体和缺失细胞中的多核糖体水平降低。间接免疫荧光表明Lcp5p主要定位于核仁。此外,针对Lcp5p的抗体特异性免疫沉淀酵母U3 snoRNA snR17,表明该蛋白质直接参与pre-rRNA加工。