A divergent transcription factor TFIIB in trypanosomes is required for RNA polymerase II-dependent spliced leader RNA transcription and cell viability
A divergent transcription factor TFIIB in trypanosomes is required for RNA polymerase II-dependent spliced leader RNA transcription and cell viability
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DOI：
10.1128/ec.5.2.293-300.2006
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发表时间：
2006-02-01
期刊：
影响因子：
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通讯作者：
Bellofatto, V
中科院分区：
文献类型：
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作者：
Palenchar, JB;Liu, WZ;Bellofatto, V
锥虫中RNA聚合酶II的转录偏离了标准的真核生物范式。基因被多顺反子转录，随后被切割成功能性mRNA，需要来自短转录物的加帽的39个核苷酸的前导RNA（剪接的前导（SL）RNA）的反式剪接。唯一确定的锥虫RNA聚合酶II启动子是SL RNA基因的启动子。我们以前已经表明，SL RNA的转录需要不同的锥虫同源物的RNA聚合酶II，TATA结合蛋白，和小核RNA（snRNA）激活蛋白复合物。在其他真核生物中，TFIIB是mRNA和聚合酶II依赖性snRNA转录的额外关键组分。我们已经确定了一个分歧的同源物通常高度保守的基础转录因子，TFIIB，从致病性寄生虫布氏锥虫。T.布鲁氏菌TFIIB（TbTFIIB）与锥虫TATA结合蛋白和RNA聚合酶II直接相互作用，证实了其身份。在功能上，体外转录研究表明TbTFIIB在SL RNA基因转录中是不可或缺的。RNA干扰（RNAi）研究证实了TbTFIIB的基本性质，因为这种蛋白质的耗尽导致寄生虫的生长停滞。此外，从TbTFIIB耗尽的寄生虫制备的核提取物，在RNAi诱导后，需要重组TbTFIIB来支持剪接前导转录。从TbTFIIB研究中收集的信息进一步加深了我们对SL RNA基因转录和锥虫中难以捉摸的整体转录过程的理解。
Transcription by RNA polymerase II in trypanosomes deviates from the standard eukaryotic paradigm. Genes are transcribed polycistronically and subsequently cleaved into functional mRNAs, requiring trans splicing of a capped 39-nucleotide leader RNA derived from a short transcript, the spliced leader (SL) RNA. The only identified trypanosome RNA polymerase II promoter is that of the SL RNA gene. We have previously shown that transcription of SL RNA requires divergent trypanosome homologs of RNA polymerase II, TATA binding protein, and the small nuclear RNA (snRNA)-activating protein complex. In other eukaryotes, TFIIB is an additional key component of transcription for both mRNAs and polymerase II-dependent snRNAs. We have identified a divergent homolog of the usually highly conserved basal transcription factor, TFIIB, from the pathogenic parasite Trypanosoma brucei. T. brucei TFIIB (TbTFIIB) interacted directly with the trypanosome TATA binding protein and RNA pollymerase II, confirming its identity. Functionally, in vitro transcription studies demonstrated that TbTFIIB is indispensable in SL RNA gene transcription. RNA interference (RNAi) studies corroborated the essential nature of TbTFIIB, as depletion of this protein led to growth arrest of parasites. Furthermore, nuclear extracts prepared from parasites depleted of TbTFIIB, after the induction of RNAi, required recombinant TbTFIIB to support spliced leader transcription. The information gleaned from TbTFIIB studies furthers our understanding of SL RNA gene transcription and the elusive overall transcriptional processes in trypanosomes.