Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK.
EMBO J. 2011 May 10;30(12):2420-30. doi: 10.1038/emboj.2011.148.
2'-O-methylation of eukaryotic ribosomal RNA (r)RNA, essential for ribosome function, is catalysed by box C/D small nucleolar (sno)RNPs. The RNA components of these complexes (snoRNAs) contain one or two guide sequences, which, through base-pairing, select the rRNA modification site. Adjacent to the guide sequences are protein-binding sites (the C/D or C'/D' motifs). Analysis of >2000 yeast box C/D snoRNAs identified additional conserved sequences in many snoRNAs that are complementary to regions adjacent to the rRNA methylation site. This 'extra base-pairing' was also found in many human box C/D snoRNAs and can stimulate methylation by up to five-fold. Sequence analysis, combined with RNA-protein crosslinking in Saccharomyces cerevisiae, identified highly divergent box C'/D' motifs that are bound by snoRNP proteins. In vivo rRNA methylation assays showed these to be active. Our data suggest roles for non-catalytic subunits (Nop56 and Nop58) in rRNA binding and support an asymmetric model for box C/D snoRNP organization. The study provides novel insights into the extent of the snoRNA-rRNA interactions required for efficient methylation and the structural organization of the snoRNPs.
真核核糖体 RNA(r)RNA 的 2'-O-甲基化对于核糖体功能至关重要，它由框 C/D 小核仁(sno)RNP 催化。这些复合物的 RNA 成分（snoRNA）包含一个或两个引导序列，通过碱基配对，选择 rRNA 修饰位点。引导序列旁边是蛋白结合位点（C/D 或 C'/D' 基序）。对 >2000 种酵母框 C/D snoRNA 的分析确定了许多 snoRNA 中额外的保守序列，这些序列与 rRNA 甲基化位点相邻的区域互补。这种“额外的碱基配对”也存在于许多人类框 C/D snoRNA 中，可以将甲基化刺激提高五倍。序列分析结合酿酒酵母中的 RNA-蛋白交联，鉴定了高度分化的框 C'/D' 基序，由 snoRNP 蛋白结合。体内 rRNA 甲基化测定表明这些基序是活性的。我们的数据表明非催化亚基（Nop56 和 Nop58）在 rRNA 结合中起作用，并支持框 C/D snoRNP 组织的不对称模型。该研究为有效甲基化所需的 snoRNA-rRNA 相互作用的程度以及 snoRNP 的结构组织提供了新的见解。
