Tycowski K T, You Z H, Graham P J, Steitz J A
Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536, USA.
Mol Cell. 1998 Nov;2(5):629-38. doi: 10.1016/s1097-2765(00)80161-6.
The vertebrate spliceosomal snRNAs are highly modified by pseudouridylation and 2'-O-methylation. We have identified novel conserved small RNAs that can direct addition of two methyl groups in U6 snRNA, at A47 and C77. These guide RNAs, mgU6-47 (methylation guide for U6 snRNA residue 47) and mgU6-77 contain boxes C, C', D, and D' and associate with fibrillarin. Each RNA can form a duplex with U6 snRNA positioning A47 and C77 for 2'-O-methylation. The antisense element of mgU6-77 can also position C2970 of 28S rRNA for 2'-O-methylation. Depletion of mgU6-77 from Xenopus oocytes prevents 2'-O-methylation of both C77 in U6 and C2970 in 28S; methylation can be restored by injecting in vitro transcribed mgU6-77. Thus, mgU6-77 appears to function in the 2'-O-methylation of two distinct classes of cellular RNA, snRNA, and rRNA.
脊椎动物剪接体小核仁RNA（snRNAs）通过假尿苷化和2'-O-甲基化进行高度修饰。我们已经鉴定出了新型保守小RNA，它们可以指导在U6 snRNA的A47和C77位点添加两个甲基基团。这些引导RNA，即mgU6-47（U6 snRNA第47位残基的甲基化引导物）和mgU6-77，含有C、C'、D和D'框，并与纤维原蛋白结合。每个RNA都能与U6 snRNA形成双链体，将A47和C77定位以进行2'-O-甲基化。mgU6-77的反义元件还能将28S rRNA的C2970定位以进行2'-O-甲基化。从非洲爪蟾卵母细胞中去除mgU6-77可阻止U6中的C77和28S中的C2970的2'-O-甲基化；通过注射体外转录的mgU6-77可恢复甲基化。因此，mgU6-77似乎在两类不同的细胞RNA，即snRNA和rRNA的2'-O-甲基化中发挥作用。
