The fragile X syndrome repeats form RNA hairpins that do not activate the interferon-inducible protein kinase, PKR, but are cut by Dicer
The fragile X syndrome repeats form RNA hairpins that do not activate the interferon-inducible protein kinase, PKR, but are cut by Dicer
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DOI：
10.1093/nar/gkg818
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发表时间：
2003-11-01
影响因子：
14.9
通讯作者：
Usdin, K
中科院分区：
文献类型：
--
作者：
Handa, V;Saha, T;Usdin, K
我们在这里表明，在生理上合理的条件下，CGG重复RNA容易形成发夹。与形成发夹和四链体的复杂混合物的DNA对应物相反，r（CGG）（22）形成单个稳定的发夹，即使在低pH下也没有任何其他折叠结构的证据。在脆性X综合征前突变等位基因中发现的具有序列（CGG）（9）AGG（CGG）（12）AGG（CGG）（97）的RNA形成许多不同的发夹。最突出的发夹形成在重复序列的3'部分，并涉及97个不间断的CGG重复序列。与1型强直性肌营养不良重复序列形成的CUG-RNA发夹相反，我们没有发现CGG-RNA发夹激活PKR的证据，PKR是一种由广泛的双链RNA激活的干扰素诱导的蛋白激酶。然而，我们确实表明CGG-RNA被人Dicer酶消化，尽管效率低下，这是RNA干扰对基因表达影响的核心步骤。这些数据为CGG-RNA的毒性作用提供了线索，CGG-RNA被认为发生在脆性X前突变携带者中。此外，RNA发夹也可以解释40 S核糖体亚基的停滞，这被认为有助于脆性X前突变和完全突变等位基因的翻译缺陷。
We show here that under physiologically reasonable conditions, CGG repeats in RNA readily form hairpins. In contrast to its DNA counterpart that forms a complex mixture of hairpins and tetraplexes, r(CGG)(22) forms a single stable hairpin with no evidence for any other folded structure even at low pH. RNA with the sequence (CGG)(9)AGG (CGG)(12)AGG(CGG)(97), found in a fragile X syndrome pre-mutation allele, forms a number of different hairpins. The most prominent hairpin forms in the 3' part of the repeat and involves the 97 uninterrupted CGG repeats. In contrast to the CUG-RNA hairpins formed by myotonic dystrophy type 1 repeats, we found no evidence that CGG-RNA hairpins activate PKR, the interferon-inducible protein kinase that is activated by a wide range of double-stranded RNAs. However, we do show that the CGG-RNA is digested, albeit inefficiently, by the human Dicer enzyme, a step central to the RNA interference effect on gene expression. These data provide clues to the basis of the toxic effect of CGG-RNA that is thought to occur in fragile X pre-mutation carriers. In addition, RNA hairpins may also account for the stalling of the 40S ribosomal subunit that is thought to contribute to the translation deficit in fragile X pre-mutation and full mutation alleles.