Elela S A, Igel H, Ares M
Biology Department, University of California, Santa Cruz 95064 ,USA.
Cell. 1996 Apr 5;85(1):115-24. doi: 10.1016/s0092-8674(00)81087-9.
A yeast gene homologous to bacterial RNase III (RNT1) encodes a double-strand-specific endoribonuclease essential for ribosome synthesis. Two rRNA processing events are blocked in cells temperature sensitive for RNT1: cleavage at the snoRNA-dependent AO site in the 5' ETS and cleavage in the 3' ETS. Recombinant RNT1 protein accurately cleaves a synthetic 5' ETS RNA at AO site in vitro, in the absence of snoRNA or other factors. A synthetic 3' ETS substrate is specifically cleaved at a site 21 nt downstream of the 3' end 28S rRNA. These observations show that a protein endonuclease collaborates with snoRNAs in eukaryotic rRNA processing and exclude a catalytic role for snoRNAs at certain pre-rRNA cleavage.
一个与细菌核糖核酸酶III（RNT1）同源的酵母基因编码一种对核糖体合成至关重要的双链特异性核糖核酸内切酶。在对RNT1温度敏感的细胞中，两个rRNA加工事件受阻：5'ETS中依赖于snoRNA的AO位点的切割以及3'ETS中的切割。重组RNT1蛋白在体外，在没有snoRNA或其他因子的情况下，能准确地在AO位点切割合成的5'ETS RNA。一种合成的3'ETS底物在28S rRNA 3'端下游21个核苷酸处的位点被特异性切割。这些观察结果表明，一种蛋白质内切酶在真核生物rRNA加工中与snoRNAs协同作用，并排除了snoRNAs在某些前体rRNA切割中的催化作用。
