Kennedy Scott, Wang Duo, Ruvkun Gary
Department of Molecular Biology, Massachusetts General Hospital and Department of Genetics, Harvard Medical School, Boston, Massachusetts 02114, USA.
Nature. 2004 Feb 12;427(6975):645-9. doi: 10.1038/nature02302.
In many organisms, introducing double-stranded RNA (dsRNA) causes the degradation of messenger RNA that is homologous to the trigger dsRNA--a process known as RNA interference. The dsRNA is cleaved into short interfering RNAs (siRNAs), which hybridize to homologous mRNAs and induce their degradation. dsRNAs vary in their ability to trigger RNA interference: many mRNA-targeting dsRNAs show weak phenotypes, and nearly all mRNAs of the Caenorhabditis elegans nervous system are refractory to RNA interference. C. elegans eri-1 was identified in a genetic screen for mutants with enhanced sensitivity to dsRNAs. Here we show that eri-1 encodes an evolutionarily conserved protein with domains homologous to nucleic-acid-binding and exonuclease proteins. After exposure to dsRNA or siRNAs, animals with eri-1 mutations accumulate more siRNAs than do wild-type animals. C. elegans ERI-1 and its human orthologue degrade siRNAs in vitro. In the nematode worm, ERI-1 is predominantly cytoplasmic and is expressed most highly in the gonad and a subset of neurons, suggesting that ERI-1 siRNase activity suppresses RNA interference more intensely in these tissues. Thus, ERI-1 is a negative regulator that may normally function to limit the duration, cell-type specificity or endogenous functions of RNA interference.
在许多生物体中，引入双链RNA（dsRNA）会导致与触发dsRNA同源的信使RNA降解——这一过程被称为RNA干扰。dsRNA被切割成短干扰RNA（siRNA），后者与同源mRNA杂交并诱导其降解。dsRNA触发RNA干扰的能力各不相同：许多靶向mRNA的dsRNA表现出较弱的表型，而且秀丽隐杆线虫神经系统的几乎所有mRNA都对RNA干扰具有抗性。秀丽隐杆线虫eri-1是在对dsRNA敏感性增强的突变体进行的遗传筛选中鉴定出来的。我们在此表明，eri-1编码一种进化上保守的蛋白质，其结构域与核酸结合蛋白和核酸外切酶蛋白同源。暴露于dsRNA或siRNA后，eri-1突变的动物比野生型动物积累更多的siRNA。秀丽隐杆线虫ERI-1及其人类同源物在体外可降解siRNA。在这种线虫中，ERI-1主要存在于细胞质中，在性腺和一部分神经元中表达水平最高，这表明ERI-1的siRNase活性在这些组织中更强烈地抑制RNA干扰。因此，ERI-1是一种负调控因子，其正常功能可能是限制RNA干扰的持续时间、细胞类型特异性或内源性功能。
