Yip W S Vincent, Shigematsu Hideki, Taylor David W, Baserga Susan J
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
Department of Cellular and Molecular Physiology, Yale University, New Haven, CT 06520, USA RIKEN Center for Life Science Technology, Yokohama, Kanagawa 230-0045, Japan.
Nucleic Acids Res. 2016 Oct 14;44(18):8976-8989. doi: 10.1093/nar/gkw576. Epub 2016 Jun 24.
Ribosomal RNA (rRNA) modifications are essential for ribosome function in all cellular organisms. Box C/D small (nucleolar) ribonucleoproteins [s(no)RNPs] catalyze 2'-O-methylation, one rRNA modification type in Eukarya and Archaea. Negatively stained electron microscopy (EM) models of archaeal box C/D sRNPs have demonstrated the dimeric sRNP (di-sRNP) architecture, which has been corroborated by nuclear magnetic resonance (NMR) studies. Due to limitations of the structural techniques, the orientation of the box C/D sRNAs has remained unclear. Here, we have used cryo-EM to elucidate the sRNA orientation in a M. jannaschii box C/D di-sRNP. The cryo-EM reconstruction suggests a parallel orientation of the two sRNAs. Biochemical and structural analyses of sRNPs assembled with mutant sRNAs indicate a potential interaction between the sRNA stem ends. Our results suggest that the parallel arrangement of the sRNAs juxtaposes their stem ends into close proximity to allow for a stabilizing interaction that helps maintain the di-sRNP architecture.
核糖体RNA（rRNA）修饰对于所有细胞生物的核糖体功能至关重要。C/D盒小（核仁）核糖核蛋白[s(no)RNPs]催化2'-O-甲基化，这是真核生物和古细菌中的一种rRNA修饰类型。古细菌C/D盒sRNPs的负染电子显微镜（EM）模型已经展示了二聚体sRNP（di-sRNP）结构，这已得到核磁共振（NMR）研究的证实。由于结构技术的局限性，C/D盒sRNAs的方向仍不明确。在这里，我们使用冷冻电镜来阐明詹氏甲烷球菌C/D盒di-sRNP中sRNA的方向。冷冻电镜重建表明两个sRNAs呈平行方向。对与突变sRNAs组装的sRNPs进行的生化和结构分析表明，sRNA茎端之间存在潜在相互作用。我们的结果表明，sRNAs的平行排列使它们的茎端并列靠近，从而允许一种稳定相互作用，有助于维持di-sRNP结构。
