近日,，PNAS在線發(fā)表了中科院上海生科院營(yíng)養(yǎng)科學(xué)研究所馮英研究組的最新研究進(jìn)展：“Far upstream element-binding protein 1 and RNA secondary structure both mediate second-step splicing repression”,。該研究揭示了RNA二級(jí)結(jié)構(gòu)在剪接調(diào)控中的新機(jī)制,，并首次證明了MYC調(diào)控蛋白FUBP1同樣具有剪接調(diào)控活性,。

RNA剪接是連接轉(zhuǎn)錄與翻譯的重要橋梁，也是生物體蛋白質(zhì)多樣性的重要保證,。在真核生物中，mRNA前體被剪接成為成熟的mRNA一般需要在多種蛋白質(zhì)及snRNA的幫助下,，經(jīng)歷兩步轉(zhuǎn)酯剪接反應(yīng)來(lái)完成,。目前對(duì)于第二步剪接反應(yīng)的調(diào)控知之甚少。

馮英研究組在前期工作中發(fā)現(xiàn)了一種特殊的mRNA前體,，該前體在剪接反應(yīng)已經(jīng)開啟的情況下,，僅將轉(zhuǎn)酯反應(yīng)進(jìn)行到第一步即停止，第二步反應(yīng)則被完全抑制,。馮英研究員指導(dǎo)的博士生李璜等研究人員對(duì)造成這一特殊現(xiàn)象的機(jī)制進(jìn)行了深入研究,。利用多種體外、體內(nèi)的剪接模型以及定點(diǎn)突變,，研究組發(fā)現(xiàn)剪接位點(diǎn)附近形成的RNA二級(jí)結(jié)構(gòu)會(huì)顯著抑制第二步剪接反應(yīng)的發(fā)生,；同時(shí)還發(fā)現(xiàn)單鏈DNA結(jié)合蛋白FUBP1通過(guò)與剪接沉默子（ESS）元件結(jié)合，能夠有效抑制第二步剪接反應(yīng)的發(fā)生,。在體外剪接環(huán)境中降低FUBP1蛋白水平,，可以有效促進(jìn)第二步剪接反應(yīng)的效率；而在細(xì)胞水平上改變FUBP1的含量不僅會(huì)影響該mRNA前體的剪接,，還會(huì)改變一系列內(nèi)源mRNA前體的剪接模式,。

該研究加深了人們對(duì)于RNA高級(jí)結(jié)構(gòu)與剪接調(diào)控之間關(guān)系的理解，首次證明了MYC調(diào)控蛋白FUBP1也同樣具有調(diào)控剪接反應(yīng)的活性,，這種剪接調(diào)控能力很可能與FUBP1在多種重要生理過(guò)程中發(fā)揮的功能相關(guān),。

該項(xiàng)目得到了中科院,、國(guó)家自然科學(xué)基金委、科技部及上海市科委項(xiàng)目的支持,。（生物谷Bioon.com）

doi:10.1073/pnas.1310607110
PMC:
PMID:
Far upstream element-binding protein 1 and RNA secondary structure both mediate second-step splicing repression

Huang Lia, Zhijia Wanga, Xuexia Zhoua, Yuanming Chenga, Zhiqin Xiea, James L. Manleyb,1, and Ying Fenga,c,1

Splicing of mRNA precursors consists of two steps that are almost invariably tightly coupled to facilitate efficient generation of spliced mRNA. However, we described previously a splicing substrate that is completely blocked after the first step. We have now investigated the basis for this unusual second-step inhibition and unexpectedly elucidated two independent mechanisms. One involves a stem–loop structure located downstream of the 3′splice site, and the other involves an exonic splicing silencer (ESS) situated 3′ to the structure. Both elements contribute to the second-step block in vitro and also cause exon skipping in vivo. Importantly, we identified far upstream element-binding protein 1 (FUBP1), a single-stranded DNA- and RNA-binding protein not previously implicated in splicing, as a strong ESS binding protein, and several assays implicate it in ESS function. We demonstrate using depletion/add-back experiments that FUBP1 acts as a second-step repressor in vitro and show by siRNA-mediated knockdown and overexpression assays that it modulates exon inclusion in vivo. Together, our results provide additional insights into splicing control, and identify FUBP1 as a splicing regulator.