Daugeron M C, Kressler D, Linder P
Département de Biochimie médicale, Centre Medical Universitaire, Université de Genève, Switzerland.
RNA. 2001 Sep;7(9):1317-34. doi: 10.1017/s1355838201010640.
Ribosome synthesis is a highly complex process and constitutes a major cellular activity. The biogenesis of this ribonucleoprotein assembly requires a multitude of protein trans-acting factors including several putative ATP-dependent RNA helicases of the DEAD-box and related protein families. Here we show that the previously uncharacterized Saccharomyces cerevisiae open reading frame YLR276C, hereafter named DBP9 (DEAD-box protein 9), encodes an essential nucleolar protein involved in 60S-ribosomal-subunit biogenesis. Genetic depletion of Dbp9p results in a deficit in 60S ribosomal subunits and the appearance of half-mer polysomes. This terminal phenotype is likely due to the instability of early pre-ribosomal particles, as evidenced by the low steady-state levels and the decreased synthesis of the 27S precursors to mature 25S and 5.8S rRNAs. In agreement with a role of Dbp9p in 60S subunit synthesis, we find that increased Dbp9p dosage efficiently suppresses certain dbp6 alleles and that dbp6/dbp9 double mutants show synthetic lethality. Furthermore, Dbp6p and Dbp9p weakly interact in a yeast two-hybrid assay. Altogether, our findings indicate an intimate functional interaction between Dbp6p and Dbp9p during the process of 60S-ribosomal-subunit assembly.
核糖体合成是一个高度复杂的过程，是细胞的一项主要活动。这种核糖核蛋白组装体的生物发生需要多种蛋白质反式作用因子，包括DEAD-box及相关蛋白家族中几种假定的ATP依赖型RNA解旋酶。在此，我们表明，酿酒酵母中以前未被鉴定的开放阅读框YLR276C，以下命名为DBP9（DEAD-box蛋白9），编码一种参与60S核糖体亚基生物发生的必需核仁蛋白。Dbp9p的基因缺失导致60S核糖体亚基缺乏，并出现半聚核糖体。这种终末表型可能是由于早期核糖体前体颗粒的不稳定性，成熟25S和5.8S rRNA的27S前体的低稳态水平和合成减少证明了这一点。与Dbp9p在60S亚基合成中的作用一致，我们发现增加Dbp9p的剂量能有效抑制某些dbp6等位基因，并且dbp6/dbp9双突变体表现出合成致死性。此外，在酵母双杂交试验中，Dbp6p和Dbp9p有微弱的相互作用。总之，我们的研究结果表明在60S核糖体亚基组装过程中Dbp6p和Dbp9p之间存在密切的功能相互作用。
