The 3' end of yeast 5.8S rRNA is generated by an exonuclease processing mechanism
The 3' end of yeast 5.8S rRNA is generated by an exonuclease processing mechanism
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DOI：
10.1101/gad.10.4.502
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发表时间：
1996-02-15
影响因子：
10.5
通讯作者：
Tollervey, D
中科院分区：
文献类型：
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作者：
Mitchell, P;Petfalski, E;Tollervey, D
真核rRNA(5S rRNA除外)是由连续的Pre-rRNA前体通过一系列复杂的加工反应合成的。酵母5.8S rRNA的最终成熟涉及一个3‘延伸的7S前体的加工，该前体含有类似于内部转录间隔区2(ITS2)的140个核苷酸。在携带温度敏感(Ts)rrp4-1突变的酵母菌株中，观察到5.8S rRNA物种，其3‘端的长度可变延伸至7S Pre-rRNA的3’端。这些3‘-延伸的5.8S rRNA在rrp4-1菌株中低水平地观察到，在允许生长的条件下，在转移到不允许的温度时，它们的丰度增加。通过对rrp4-1菌株ts生长表型的互补，克隆了rrp4基因。RRP4编码一种预测分子质量为39kD的必需蛋白。免疫沉淀的Rrp4p在体外表现出3‘-gt；5’外切核糖核酸酶活性，需要带有3‘-末端羟基的RNA，并释放核苷5’单磷酸。我们认为，7S前rRNA是通过Rrp4p参与的3‘-gt；5’外切酶活性加工成5.8S rRNA的。在人和裂殖酵母中都发现了Rrp4p的同源物(分别为43%和52%)，这表明5.8S rRNA 3‘端的形成机制在真核生物中是保守的。
Eukaryotic rRNAs (with the exception of 5S rRNA) are synthesized from a contiguous pre-rRNA precursor by a complex series of processing reactions. Final maturation of yeast 5.8S rRNA involves processing of a 3'-extended, 7S precursor that contains similar to 140 nucleotides of the internal transcribed spacer 2 (ITS2) region. In yeast strains carrying the temperature-sensitive (ts) rrp4-1 mutation, 5.8S rRNA species were observed with 3' extensions of variable length extending up to the 3' end of the 7S pre-rRNA. These 3'-extended 5.8S rRNA species were observed at low levels in rrp4-1 strains under conditions permissive for growth and increased in abundance upon transfer to the nonpermissive temperature. The RRP4 gene was cloned by complementation of the ts growth phenotype of rrp4-1 strains. RRP4 encodes an essential protein of 39-kD predicted molecular mass. Immunoprecipitated Rrp4p exhibited a 3' --> 5' exoribonuclease activity in vitro that required RNA with a 3'-terminal hydroxyl group and released nucleoside 5' monophosphates. We conclude that the 7S pre-rRNA is processed to 5.8S rRNA by a 3' --> 5' exonuclease activity involving Rrp4p. Homologs of Rrp4p are found in both humans and the fission yeast Schizosaccaromyces pombe (43% and 52% identity, respectively), suggesting that the mechanism of 5.8S rRNA 3' end formation has been conserved throughout eukaryotes.