6月22日,，國際學(xué)術(shù)期刊《Nucleic Acids Research》在線發(fā)表了生化與細(xì)胞所惠靜毅研究組題為 “YB-1 binds to CAUC motifs and stimulates exon inclusion by enhancing the recruitment of U2AF to weak polypyrimidine tracts” 的研究論文,。該研究結(jié)果揭示了YB-1蛋白在調(diào)控3’ 剪接位點識別中的重要功能。
YB-1蛋白是一個多功能的DNA/RNA 結(jié)合蛋白,，它在轉(zhuǎn)錄和翻譯調(diào)控中均能發(fā)揮重要作用,。近年來的一些報道表明，YB-1是一個剪接體相關(guān)蛋白并參與可變剪接,，但是它調(diào)控剪接的分子機(jī)制并不清楚,。本項研究發(fā)現(xiàn)YB-1能夠特異地結(jié)合含有CAUC或CACC核心序列的RNA，并證明了CAUC序列是一類新的剪接增強(qiáng)子,。利用細(xì)胞表面吸附分子CD44基因作為模型,，闡明YB-1通過結(jié)合CD44可變外顯子5（v5）中和其上游多聚嘧啶位點中的CAUC序列促進(jìn)外顯子v5剪接的作用方式。U2AF65是識別3’剪接位點中多聚嘧啶區(qū)的關(guān)鍵剪接因子,，有意思的是,，U2AF65并不直接結(jié)合外顯子v5上游的多聚嘧啶區(qū)。進(jìn)一步的實驗結(jié)果揭示了YB-1識別CAUC序列,，并通過直接結(jié)合U2AF蛋白招募U2AF65到弱的多聚嘧啶區(qū),，從而激活外顯子剪接的分子機(jī)制。哺乳動物基因的3’剪接位點順序十分不保守,，大量內(nèi)含子的3’剪接位點中多聚嘧啶區(qū)缺乏U2AF65結(jié)合序列,，這些3’剪接位點是如何被識別的一直是大家關(guān)心的問題。本項研究提示了其它RNA結(jié)合蛋白也可能通過這一方式參與了弱的3’剪接位點的識別,，相關(guān)研究正在深入開展,。
該課題由博士生魏文娟和牟世榮在惠靜毅研究員指導(dǎo)下完成。課題得到國家科技部,、國家自然科學(xué)基金委,、中國科學(xué)院以及上海市科委等經(jīng)費資助。(生物谷Bioon.com）
doi：10.1093/nar/gks579
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PMID:
YB-1 binds to CAUC motifs and stimulates exon inclusion by enhancing the recruitment of U2AF to weak polypyrimidine tracts
Wen-Juan Wei1,， Shi-Rong Mu1,， Monika Heiner1， Xing Fu1,， Li-Juan Cao1,， Xiu-Feng Gong1,， Albrecht Bindereif2 and Jingyi Hui1，*
Abstract
The human Y box-binding protein-1 (YB-1) is a deoxyribonucleic acid (DNA)/ribonucleic acid (RNA)-binding protein with pleiotropic functions. Besides its roles in the regulation of transcription and translation,， several recent studies indicate that YB-1 is a spliceosome-associated protein and is involved in alternative splicing,， but the underlying mechanism has remained elusive. Here， we define both CAUC and CACC as high-affinity binding motifs for YB-1 by systematic evolution of ligands by exponential enrichment (SELEX) and demonstrate that these newly defined motifs function as splicing enhancers. Interestingly,， on the endogenous CD44 gene,， YB-1 appears to mediate a network interaction to activate exon v5 inclusion via multiple CAUC motifs in both the alternative exon and its upstream polypyrimidine tract. We provide evidence that YB-1 activates splicing by facilitating the recruitment of U2AF65 to weak polypyrimidine tracts through direct protein–protein interactions. Together， these findings suggest a vital role of YB-1 in activating a subset of weak 3′ splice sites in mammalian cells.
