Kiss-László Z, Henry Y, Kiss T
Laboratoire de Biologie Moléculaire Eucaryote du Centre National de la Recherche Scientifique, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex, France.
EMBO J. 1998 Feb 2;17(3):797-807. doi: 10.1093/emboj/17.3.797.
Site-specific 2'-O-ribose methylation of eukaryotic rRNAs is guided by small nucleolar RNAs (snoRNAs). The methylation guide snoRNAs carry long perfect complementaries to rRNAs. These antisense elements are located either in the 5' half or in the 3' end region of the snoRNA, and are followed by the conserved D' or D box motifs, respectively. An uninterrupted helix formed between the rRNA and the antisense element of the snoRNA, in conjunction with the adjacent D' or D box, constitute the recognition signal for the putative methyltransferase. Here, we have identified an additional essential box element common to methylation guide snoRNAs, termed the C' box. We show that the C' box functions in concert with the D' box and plays a crucial role in the methyltransfer reaction directed by the upstream antisense element and the D' box. We also show that an internal fragment of U24 methylation guide snoRNA, encompassing the upstream antisense element and the D' and C' box motifs, can support the site-specific methylation of rRNA. This strongly suggests that the C box of methylation guide snoRNAs plays an essential role in the methyltransfer reaction guided by the 3'-terminal antisense element and the D box of the snoRNA.
真核生物核糖体RNA（rRNA）的位点特异性2'-O-核糖甲基化由小核仁RNA（snoRNA）引导。甲基化引导snoRNA与rRNA具有长的完全互补序列。这些反义元件位于snoRNA的5'半段或3'末端区域，分别接着保守的D'或D框基序。rRNA与snoRNA的反义元件之间形成的不间断螺旋，连同相邻的D'或D框，构成了假定甲基转移酶的识别信号。在此，我们鉴定出了甲基化引导snoRNA共有的另一个必需框元件，称为C'框。我们表明，C'框与D'框协同作用，在上游反义元件和D'框引导的甲基转移反应中起关键作用。我们还表明，U24甲基化引导snoRNA的一个内部片段，包含上游反义元件以及D'和C'框基序，能够支持rRNA的位点特异性甲基化。这有力地表明，甲基化引导snoRNA的C框在由snoRNA的3'-末端反义元件和D框引导的甲基转移反应中起重要作用。
