Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia.
PLoS One. 2012;7(9):e44157. doi: 10.1371/journal.pone.0044157. Epub 2012 Sep 12.
Two RNAs (4.5SH and 4.5SI) with unknown functions share a number of features: short length (about 100 nt), transcription by RNA polymerase III, predominately nuclear localization, the presence in various tissues, and relatively narrow taxonomic distribution (4 and 3 rodent families, respectively). It was reported that 4.5SH RNA turns over rapidly, whereas 4.5SI RNA is stable in the cell, but their lifetimes remained unknown. We showed that 4.5SH is indeed short-lived (t(1/2)18 min) and 4.5SI is long-lived (t(1/2)22 h) in Krebs ascites carcinoma cells. The RNA structures specifying rapid or slow decay of different small cellular RNAs remain unstudied. We searched for RNA structural features that determine the short lifetime of 4.5SH in comparison with the long lifetime of 4.5SI RNA. The sequences of genes of 4.5SH and 4.5SI RNAs were altered and human cells (HeLa) were transfected with these genes. The decay rate of the original and altered RNAs was measured. The complementarity of 16-nt end regions of 4.5SI RNA proved to contribute to its stability in cells, whereas the lack of such complementarity in 4.5SH RNA caused its rapid decay. Possible mechanisms of the phenomenon are discussed.
两种具有未知功能的 RNA（4.5SH 和 4.5SI）具有许多共同特征：长度较短（约 100 个核苷酸）、由 RNA 聚合酶 III 转录、主要定位于核内、在各种组织中存在、以及相对狭窄的分类分布（分别为 4 种和 3 种啮齿动物科）。据报道，4.5SH RNA 周转迅速，而 4.5SI RNA 在细胞中稳定，但它们的寿命仍不清楚。我们表明，4.5SH 在 Krebs 腹水癌细胞中确实是短命的（t(1/2)18 分钟），而 4.5SI 是长寿命的（t(1/2)22 小时）。指定不同小细胞 RNA 快速或缓慢衰减的 RNA 结构特征仍未得到研究。我们搜索了决定 4.5SH 短寿命与 4.5SI RNA 长寿命的 RNA 结构特征。改变了 4.5SH 和 4.5SI RNA 基因的序列，并将这些基因转染入人细胞（HeLa）。测量了原始和改变的 RNA 的衰减率。4.5SI RNA 的 16 个核苷酸末端区域的互补性被证明有助于其在细胞中的稳定性，而 4.5SH RNA 中缺乏这种互补性导致其快速衰减。讨论了可能的机制。
