The spacing between functional cis-elements of U3 snoRNA is critical for rRNA processing
The spacing between functional cis-elements of U3 snoRNA is critical for rRNA processing
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DOI：
10.1006/jmbi.2000.3798
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发表时间：
2000-06-30
影响因子：
5.6
通讯作者：
Gerbi, SA
中科院分区：
文献类型：
--
作者：
Borovjagin, AV;Gerbi, SA
通过非洲爪哇卵母细胞耗竭/挽救实验，分析了非洲爪哇U3小核仁RNA(SnoRNA)的序列和结构特征，发现snoRNA是非洲爪哇卵母细胞裂解前rRNA形成18S rRNA所必需的。突变结果表明，U3结构域I的假定茎对于18 S rRNA的加工是不必要的。当U3尚未与前rRNA结合时，提出了与早期实验数据一致的结构域I的结构模型。关于它在rRNA加工中的作用，新发现的一个元件(5‘铰链)对18 S rRNA的形成起着重要的作用，但不如非洲爪哇U3 snoRNA的3’铰链区那么关键。碱基配对被认为发生在U3的5‘铰链和3’铰链以及外部转录间隔区(ETS)的互补区之间；这些相互作用在系统发育上是保守的，并且与以前在酵母(5‘铰链-ETS)和锥体(3’铰链-ETS)中描述的那些同源。提出了一个模型，其中U3 snoRNA的5‘和3’铰链与前rRNA的Ets的碱基配对有助于正确定位U3盒A‘+A在rRNA加工中的功能。与早期关于酵母的建议一样，非洲爪哇的A‘和A框可能与前rRNA中的18个S序列碱基配对。我们首次在任何系统中提供了直接的实验证据，证明在18 S rRNA形成中，A‘盒对于U3 snoRNA功能是必不可少的。对插入和缺失的分析表明，U3元件之间的间距是重要的，表明它们同时与Ets和18个S前rRNA区域碱基配对。(C)2000年学术出版社。
The sequences and structural features of Xenopus laevis U3 small nucleolar RNA (snoRNA) necessary for pre-rRNA cleavage at sites 1 and 2 to form 18S rRNA were assayed by depletion/rescue experiments in Xenopus oocytes. Mutagenesis results demonstrated that the putative stem of U3 domain I is unnecessary for 18 S rRNA processing. A model consistent with earlier experimental data is proposed for the structure of domain I when U3 is not yet bound to pre-rRNA. For its function in rRNA processing, a newly discovered element (5' hinge) was revealed to be important but not as critical as the 3' hinge region in Xenopus U3 snoRNA for 18 S rRNA formation. Base-pairing is proposed to occur between the U3 5' hinge and 3' hinge and complementary regions in he external transcribed spacer (ETS); these interactions are phylogenetically conserved, and are homologous to those previously described in yeast (5' hinge-ETS) and trypanosomes (3' hinge-ETS). A model is presented where the base-pairing of the 5' hinge and 3' hinge of U3 snoRNA with the ETS of pre-rRNA helps to correctly position U3 boxes A' + A for their function in rRNA processing. Like an earlier proposal for yeast, boxes A' and A of Xenopus may base-pair with 18 S sequences in pre-rRNA. We present the first direct experimental evidence in any system that box A' is essential for U3 snoRNA function in 18 S rRNA formation. The analysis of insertions and deletions indicated that the spacing between the U3 elements is important, suggesting that they base-pair with the ETS and 18 S regions of pre-rRNA at the same time. (C) 2000 Academic Press.