The Bioinformatics Centre, Department of Biology and the Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark.
Nat Struct Mol Biol. 2011 Aug 7;18(9):1075-82. doi: 10.1038/nsmb.2091.
Efforts to catalog eukaryotic transcripts have uncovered many small RNAs (sRNAs) derived from gene termini and splice sites. Their biogenesis pathways are largely unknown, but a mechanism based on backtracking of RNA polymerase II (RNAPII) has been suggested. By sequencing transcripts 12-100 nucleotides in length from cells depleted of major RNA degradation enzymes and RNAs associated with Argonaute (AGO1/2) effector proteins, we provide mechanistic models for sRNA production. We suggest that neither splice site-associated (SSa) nor transcription start site-associated (TSSa) RNAs arise from RNAPII backtracking. Instead, SSa RNAs are largely degradation products of splicing intermediates, whereas TSSa RNAs probably derive from nascent RNAs protected by stalled RNAPII against nucleolysis. We also reveal new AGO1/2-associated RNAs derived from 3' ends of introns and from mRNA 3' UTRs that appear to draw from noncanonical microRNA biogenesis pathways.
为了对真核转录本进行编目，人们已经发现了许多来自基因末端和剪接位点的小 RNA（sRNA）。其生物发生途径在很大程度上是未知的，但有人提出了一种基于 RNA 聚合酶 II（RNAPII）回溯的机制。通过对耗尽主要 RNA 降解酶和 Argonaute（AGO1/2）效应蛋白相关 RNA 的细胞中长度为 12-100 个核苷酸的转录本进行测序，我们提供了 sRNA 产生的机制模型。我们认为，剪接位点相关（SSa）和转录起始位点相关（TSSa）RNA 都不是由 RNAPII 回溯产生的。相反，SSa RNA 主要是剪接中间体的降解产物，而 TSSa RNA 可能来自被停滞的 RNAPII 保护免受核酶降解的新生 RNA。我们还揭示了新的 AGO1/2 相关 RNA，它们来自内含子的 3' 端和 mRNA 3' UTR，似乎来自非典型的 microRNA 生物发生途径。
