O'Day C L, Chavanikamannil F, Abelson J
Division of Biology 147-75, California Institute of Technology, Pasadena 91125, USA.
Nucleic Acids Res. 1996 Aug 15;24(16):3201-7. doi: 10.1093/nar/24.16.3201.
We report the identification of a new gene, RRP3 (rRNA processing), which is required for pre-rRNA processing. Rrp3 is a 60.9 kDa protein that is required for maturation of the 35S primary transcript of pre-rRNA and is required for cleavages leading to mature 18S RNA. RRP3 was identified in a PCR screen for DEAD box genes. DEAD box genes are part of a large family of proteins homologous to the eukaryotic transcription factor elF-4a. Most of these proteins are RNA-dependent ATPases and some of them have RNA helicase activity. This is the third yeast DEAD box protein that has been shown to be involved in rRNA assembly, but the only one required for the processing of 18S RNA. Mutants of the two other putative helicases, Spb4 and Drsl, both show processing defects in 25S rRNA maturation. In strains where Rrp3 is depleted, 35S precursor RNA is improperly processed. Cleavage normally occurs at sites A0O, Al and A2, but in the Rrp3 depletion stain cleavage occurs between A2 and B1. Rrp3 has been purified to homogeneity and has a weak RNA-dependent ATPase activity which is not specific for rRNA.
我们报告了一个新基因RRP3（核糖体RNA加工）的鉴定，它是前体核糖体RNA加工所必需的。Rrp3是一种60.9 kDa的蛋白质，对于前体核糖体RNA的35S初级转录本的成熟是必需的，并且对于产生成熟18S RNA的切割也是必需的。RRP3是在针对DEAD盒基因的PCR筛选中鉴定出来的。DEAD盒基因是与真核转录因子elF-4a同源的一大类蛋白质的一部分。这些蛋白质中的大多数是RNA依赖性ATP酶，其中一些具有RNA解旋酶活性。这是第三个已被证明参与核糖体RNA组装的酵母DEAD盒蛋白，但却是唯一一个参与18S RNA加工所必需的蛋白。另外两个假定的解旋酶Spb4和Drsl的突变体，在25S核糖体RNA成熟过程中均显示加工缺陷。在Rrp3被耗尽的菌株中，35S前体RNA加工不当。正常情况下在A00、A1和A2位点发生切割，但在Rrp3耗尽的菌株中，切割发生在A2和B1之间。Rrp3已被纯化至同质，具有较弱的RNA依赖性ATP酶活性，且对核糖体RNA不具有特异性。
