Role of the ITS2-proximal stem and evidence for indirect recognition of processing sites in pre-rRNA processing in yeast
Role of the ITS2-proximal stem and evidence for indirect recognition of processing sites in pre-rRNA processing in yeast
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DOI：
10.1093/nar/29.10.2106
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发表时间：
2001-05-15
影响因子：
14.9
通讯作者：
Peculis, BA
中科院分区：
文献类型：
--
作者：
Côté, CA;Peculis, BA
真核生物顺式作用序列和交易因子，包括snorna。我们在酵母中使用rDNA质粒的定向诱变来鉴定its2近端茎内和侧翼的关键序列和结构元件。这种碱基配对结构存在于成熟核糖体中，形成于25S的5′端和5.8S rnas的3′端之间。之前我们证明了这种结构的形成对酵母中pre-rRNA的加工至关重要。在这里，我们发现在its2 -近端干中没有序列特异性识别元素，相反，该干的结构对处理至关重要。这个茎不能超过一个特定的长度，但在这个三段茎的不同区域有不同的长度限制。加工既不需要茎中保守的未配对核苷酸，也不需要加工位点上成熟rRNA的序列。总的来说，这些结果提示了一个测量模型，即ITS2 C2加工位点的初始裂解和随后产生成熟末端的外切酶活性的终止受到ITS2近端茎中序列和结构元件的相对位置的影响。
Eucaryotic cis-acting sequences and transacting factors, including snoRNAs. We have used directed mutagenesis of rDNA plasmids in yeast to identify critical sequence and structural elements within and flanking the ITS2-proximal stem. This base paired structure, present in the mature ribosome, is formed between the 5'-end of 25S and the 3'-end of 5.8S rRNAs. Previously we demonstrated that formation of this structure was critical for pre-rRNA processing in yeast. Here we show that there are no sequence-specific recognition elements within the ITS2-proximal stem, rather the structure of this stem is critical for processing. This stem cannot exceed a specific length, but there are different length restrictions for different regions within this tripartite stem. Neither the conserved unpaired nucleotides within the stem nor the sequence of the mature rRNA at the processing sites are required for processing. Collectively, these results suggest a measuring model whereby initial cleavage within ITS2 at the C2 processing site and termination of subsequent exonuclease activity yielding the mature termini are affected by the relative position of sequence and structural elements within the ITS2-proximal stem.