Ni J, Tien A L, Fournier M J
Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst 01003, USA.
Cell. 1997 May 16;89(4):565-73. doi: 10.1016/s0092-8674(00)80238-x.
Ten ACA yeast small nucleolar RNAs (snoRNAs) were shown to be required for site-specific synthesis of pseudouridine psi in ribosomal RNA. A common secondary folding motif for the snoRNAs and rRNA target segments predicts that site selection involves: (1) base pairing of the snoRNA with complementary rRNA elements flanking the site of modification, and (2) identification of a uridine located at a near-constant distance from the snoRNA ACA box. The model is supported by mutations showing that: (1) reducing the complementarity between the snoRNA and rRNA disrupts psi formation, and (2) altering the distance between the ACA box and target uridine causes an adjacent uridine to be modified. This discovery implies that most snoRNAs function in targeting nucleotide modification in rRNA: ribose methylation for the box C/D snoRNAs and psi formation for the ACA snoRNAs.
十种酿酒酵母小核仁RNA（snoRNA）被证明是核糖体RNA中假尿苷ψ位点特异性合成所必需的。snoRNA和rRNA靶片段的常见二级折叠基序预测位点选择涉及：（1）snoRNA与修饰位点侧翼的互补rRNA元件进行碱基配对，以及（2）识别与snoRNA ACA框距离近乎恒定的尿苷。该模型得到了突变的支持，这些突变表明：（1）降低snoRNA与rRNA之间的互补性会破坏ψ的形成，以及（2）改变ACA框与靶尿苷之间的距离会导致相邻尿苷被修饰。这一发现意味着大多数snoRNA在靶向rRNA中的核苷酸修饰中发挥作用：C/D框snoRNA负责核糖甲基化，而ACA snoRNA负责ψ的形成。
