microRNA sequencing after over-expression of SF2/ASF in Hela cell

Both splicing factors and microRNAs are important regulatory molecules that play key roles in post-transcriptional gene regulation. By miRNA deep sequencing, we identified 40 miRNAs that are differentially expressed upon ectopic overexpression of splicing factor SF2/ASF. Here we show that SF2/ASF and one of its up-regulated microRNAs (miR-7) can form a negative feedback loop: SF2/ASF promotes miR-7 maturation, and mature miR-7 in turn targets the 3' UTR of SF2/ASF to repress its translation. Enhanced microRNA expression is mediated by direct interaction between SF2/ASF and the primary miR-7 transcript to facilitate Drosha cleavage, and is independent of SF2/ASF function in splicing. Other miRNAs including miR-221 and miR-222 may also be regulated by SF2/ASF through a similar mechanism. These results underscore an unexpected function of SF2/ASF in pri-miRNA processing, and highlight the potential coordination between splicing control and miRNA-mediated gene repression in gene regulatory networks.

剪接因子与微小RNA（microRNAs）均为重要的调控分子，在转录后基因调控中发挥关键作用。本研究通过微小RNA深度测序（miRNA deep sequencing），鉴定出40个在剪接因子SF2/ASF异位过表达后呈现差异表达的微小RNA（miRNAs）。本研究证实，SF2/ASF与其一条上调的微小RNA（miR-7）可形成负反馈环路：SF2/ASF可促进miR-7的成熟过程，而成熟的miR-7则可靶向结合SF2/ASF的3'非翻译区（3' UTR）以抑制其翻译。微小RNA表达的上调是通过SF2/ASF与初级miR-7转录本的直接相互作用介导的，该相互作用可促进Drosha的切割过程，且不依赖于SF2/ASF的剪接功能。包括miR-221与miR-222在内的其他微小RNA，也可能通过类似机制受到SF2/ASF的调控。本研究结果揭示了SF2/ASF在初级微小RNA（pri-miRNA）加工过程中一项此前未被发现的功能，并凸显了基因调控网络中剪接调控与微小RNA介导的基因抑制之间潜在的协同作用。