脊髓性肌萎縮癥(Spinal Muscular Atrophy 縮寫(xiě)：SMA)系指遺傳性的神經(jīng)性肌肉疾病,，是嬰幼兒期常見(jiàn)的致死性常染色體隱性遺傳病之一,。SMA病人的運(yùn)動(dòng)神經(jīng)元生存蛋白基因之一SMN1發(fā)生丟失，而SMN2基因完好無(wú)損,。然而，SMN2基因所表達(dá)的pre-mRNA的7號(hào)外顯子（exon7）剪接效率低下,，導(dǎo)致無(wú)功能蛋白質(zhì)生成,。因此，提升7號(hào)外顯子的剪接效率成為目前臨床上治療該遺傳疾病的主要策略,。3月9日刊登在《細(xì)胞》子刊《分子細(xì)胞》上的封面論文報(bào)道了由入駐武漢東湖高新技術(shù)開(kāi)發(fā)區(qū)的武漢生命之美科技有限公司Chief Scientist張翼博士與武漢大學(xué)講座教授,、美國(guó)加州大學(xué)圣地亞哥分校教授付向東博士聯(lián)手帶領(lǐng)的武漢大學(xué)團(tuán)隊(duì)在提升7號(hào)外顯子剪接效率方面的創(chuàng)新性研究成果,。該成果被特選為該刊的封面文章。研究成果上月在線發(fā)表后即入選Faculty of 1000 Biology（生物科學(xué)評(píng)價(jià)庫(kù)）點(diǎn)評(píng),。
張翼博士和付向東博士團(tuán)隊(duì)采用RNA干擾技術(shù)從人類基因組所編碼的340個(gè)潛在RNA結(jié)合蛋白中篩選出一組抑制7號(hào)外顯子剪接的蛋白質(zhì),，其中包括核基質(zhì)因子SAF-A。該蛋白又名hnRNP U,，具有DNA和RNA雙重結(jié)合功能,，被發(fā)現(xiàn)在X-染色體失活，DNA損傷修復(fù),，生物鐘調(diào)控,，以及干細(xì)胞調(diào)控中發(fā)揮功能。該團(tuán)隊(duì)發(fā)現(xiàn)降低hnRNP U表達(dá)可以大幅提升SMN2基因7號(hào)外顯子的剪接效率,，有望為脊髓性肌萎縮癥的治療提供新靶點(diǎn),。
為了解析hnRNP U的作用機(jī)制，張博士和付博士團(tuán)隊(duì)使用轉(zhuǎn)錄組高通量測(cè)序方法（RNA-seq）和可變剪接調(diào)控?cái)?shù)據(jù)挖掘,，發(fā)現(xiàn)該蛋白調(diào)控多個(gè)基因的可變剪接,。該團(tuán)隊(duì)采用高端的CLIP-seq（紫外交聯(lián)免疫共沉淀-高通量測(cè)序）技術(shù)，解析出該蛋白在人類宮頸癌細(xì)胞轉(zhuǎn)錄組里的結(jié)合位置（他們?cè)迷摷夹g(shù)成功解析了致癌蛋白PTB的結(jié)合位置,，獲評(píng)"2010年中國(guó)十大科技進(jìn)展"新聞）,。深度數(shù)據(jù)分析揭示出該蛋白調(diào)控可變剪接的機(jī)制非常獨(dú)特，是通過(guò)與小核RNA（snRNA）結(jié)合,，而非與pre-mRNA的結(jié)合,。該團(tuán)隊(duì)證明該蛋白不但影響U2小核RNA-蛋白質(zhì)復(fù)合體（U2 snRNP）的成熟，同時(shí)調(diào)控該復(fù)合體成熟工廠"卡哈爾小體"（Cajal body）的形態(tài),。該研究成果為從全基因組層面認(rèn)識(shí)hnRNP U介導(dǎo)的基因表達(dá)調(diào)控及其生命學(xué)功能提供了大量數(shù)據(jù)和新視角,。預(yù)計(jì)會(huì)大大提升該蛋白所介導(dǎo)的基因調(diào)控在遺傳疾病、干細(xì)胞,、發(fā)育,、生物鐘以及DNA損傷修復(fù)等重要生物學(xué)領(lǐng)域的關(guān)注度，并推動(dòng)其從基礎(chǔ)研究邁向?qū)嶋H應(yīng)用的步伐,。（生物谷Bioon.com）
doi:10.1172/JCI58789
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Nuclear Matrix Factor hnRNP U/SAF-A Exerts a Global Control of Alternative Splicing by Regulating U2 snRNP Maturation
Rui Xiao, Peng Tang, Bo Yang, Jie Huang, Yu Zhou, Changwei Shao, Hairi Li, Hui Sun, Yi Zhang, Xiang-Dong Fu
The nuclear matrix-associated hnRNP U/SAF-A protein has been implicated in diverse pathways from transcriptional regulation to telomere length control to X inactivation, but the precise mechanism underlying each of these processes has remained elusive. Here, we report hnRNP U as a regulator of SMN2 splicing from a custom RNAi screen. Genome-wide analysis by CLIP-seq reveals that hnRNP U binds virtually to all classes of regulatory noncoding RNAs, including all snRNAs required for splicing of both major and minor classes of introns, leading to the discovery that hnRNP U regulates U2 snRNP maturation and Cajal body morphology in the nucleus. Global analysis of hnRNP U-dependent splicing by RNA-seq coupled with bioinformatic analysis of associated splicing signals suggests a general rule for splice site selection through modulating the core splicing machinery. These findings exemplify hnRNP U/SAF-A as a potent regulator of nuclear ribonucleoprotein particles in diverse gene expression pathways.
