Kent Tatyana, Lapik Yevgeniya R, Pestov Dimitri G
Department of Cell Biology, School of Osteopathic Medicine, University of Medicine and Dentistry of New Jersey, Stratford, New Jersey 08084, USA.
RNA. 2009 Jan;15(1):14-20. doi: 10.1261/rna.1384709. Epub 2008 Nov 24.
The 5' external transcribed spacer (5'ETS) is critical for 18S rRNA formation and is the longest noncoding region in a ribosomal RNA transcript. Here we show that processing in mouse 5'ETS involves two cleavage events. Processing at site A' corresponds to the previously described "primary cleavage," which precedes other processing steps. Processing at the novel site A0 occurs 1 kb downstream from A' yielding two new rRNA precursors: 43S and 29S. The excised 5'-A' and A'-A0 fragments are rapidly degraded under normal conditions. Depletion of the exosome component EXOSC10/PM-Scl100 (ortholog of yeast Rrp6p) results in a strong accumulation of the A'-A0 spacer fragment in mouse cells. We discuss the finding of a second processing site in mammalian 5'ETS in relation to the involvement of the U3 snoRNA in pre-rRNA processing and present a revised map of the mouse 18S rRNA processing pathway.
5' 外部转录间隔区（5'ETS）对于18S rRNA的形成至关重要，并且是核糖体RNA转录本中最长的非编码区域。在此我们表明，小鼠5'ETS的加工涉及两个切割事件。在A'位点的加工对应于先前描述的“初级切割”，它先于其他加工步骤。在新的A0位点的加工发生在A'下游1 kb处，产生两个新的rRNA前体：43S和29S。切除的5'-A'和A'-A0片段在正常条件下会迅速降解。外切体组分EXOSC10/PM-Scl100（酵母Rrp6p的直系同源物）的缺失导致小鼠细胞中A'-A0间隔区片段大量积累。我们结合U3 snoRNA参与前体rRNA加工的情况，讨论了在哺乳动物5'ETS中发现的第二个加工位点，并给出了小鼠18S rRNA加工途径的修订图谱。
