在肌萎縮側(cè)索硬化和額顳葉癡呆病人的病理組織中，RNA結(jié)合蛋白TDP-43及FUS在細(xì)胞質(zhì)中形成了不正常的凝集,，但是其作用機(jī)理還不明確,。近日，印度米蘭比可卡大學(xué)的Antonia Ratti等人研究發(fā)現(xiàn),，TDP-43和FUS能夠識(shí)別不同的轉(zhuǎn)錄產(chǎn)物,，而且差異性的調(diào)節(jié)它們的命運(yùn)。相關(guān)研究發(fā)表在3月16日的美國《生化周刊》（Journal of Biological Chemistry）上,。
在肌萎縮側(cè)索硬化和額顳葉癡呆病人的病理組織中,，RNA結(jié)合蛋白TDP-43及FUS在細(xì)胞質(zhì)中形成了不正常的凝集。已知TDP-43和FUS主要定位于細(xì)胞核內(nèi)，參與調(diào)節(jié)pre-mRNA的剪接,，但是他們也與mRNA的轉(zhuǎn)運(yùn),、穩(wěn)定性及翻譯有關(guān)。為了更好的研究它們胞漿活性,，我們利用RNA免疫沉淀以及芯片分析來確定與它們有關(guān)的mRNA,。
研究發(fā)現(xiàn)，雖然作用于相同的細(xì)胞內(nèi)通路,，它們卻結(jié)合在mRNA的不同位點(diǎn),。生物信息分析鑒定了80%的位于3'UTR TDP-43靶點(diǎn)的(UG)n一致序列模體。然而,，對于FUS,，這個(gè)結(jié)合模體還不太明確。通過體外分析,，研究人員確定,，結(jié)合在選擇性靶向3'UTRs的模體有：結(jié)合在TDP-43蛋白的Vegfa和Grn及結(jié)合FUS蛋白的Vps54、Nvl以及Taf15,。
研究表明,，TDP-43對Vegfa及Grn mRNA有著還不確定的作用，這樣的作用很可能會(huì)根本性的影響Progranulin蛋白含量,。然而FUS不會(huì)影響mRNA的穩(wěn)定性及翻譯過程,。實(shí)驗(yàn)也證明，位于TDP-43三個(gè)不同的點(diǎn)突變不會(huì)改變它對Vegfa及Grn mRNAs的親和性或者是它的表達(dá)水平,。
數(shù)據(jù)表明,，TDP-43及FUS可以識(shí)別mRNA的特異位點(diǎn)，并差異性的調(diào)節(jié)它們在運(yùn)動(dòng)神經(jīng)元樣細(xì)胞細(xì)胞質(zhì)中的命運(yùn),。這表明,，在神經(jīng)元細(xì)胞的RNA代謝和神經(jīng)元變性中，TDP-43及FUS起到了輔助作用,。（生物谷Bioon.com）
doi: 10.1074/jbc.M111.333450
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TDP-43 and FUS RNA-binding proteins bind distinct sets of cytoplasmic messenger RNAs and differently regulate their post-transcriptional fate in motoneuron-like cells
Claudia Colombrita, Elisa Onesto, Francesca Megiorni, Antonio Pizzuti, Francisco E. Baralle, Emanuele Buratti, Vincenzo Silani and Antonia Ratti
The RNA-binding proteins TDP-43 and FUS form abnormal cytoplasmic aggregates in affected tissues of patients with amyotrophic lateral sclerosis and frontotemporal lobar dementia. TDP-43 and FUS localize mainly in the nucleus where they regulate pre-mRNA splicing, but they are also involved in mRNA transport, stability and translation. To better investigate their cytoplasmic activities, we applied a RNA immunoprecipitation and chip analysis to define the mRNAs associated to TDP-43 and FUS in the cytoplasmic ribonucleoprotein complexes from motoneuronal NSC-34 cells.We found that they bind different sets of mRNAs although converging on common cellular pathways. Bioinformatical analyses identified the (UG)n consensus motif in 80% of 3'UTR sequences of TDP-43 targets, while for FUS the binding motif was less evident. By in vitro assays we validated binding to selected target 3'UTRs, including Vegfa and Grn for TDP-43, and Vps54, Nvl and Taf15 for FUS.We showed that TDP-43 has a destabilizing activity on Vegfa and Grn mRNA and may ultimately affect Progranulin protein content, while FUS does not affect mRNA stability/translation of its targets. We also demonstrated that three different point mutations in TDP-43 did not change the binding affinity for Vegfa and Grn mRNAs or their protein level.Our data indicate that TDP-43 and FUS recognize distinct sets of mRNAs and differently regulate their fate in the cytoplasm of motoneuron-like cells, therefore suggesting complementary roles in neuronal RNA metabolism and urodegeneration..
