The role of RBP10, a key post-transcriptional regulator in the development of Trypanosoma brucei
The role of RBP10, a key post-transcriptional regulator in the development of Trypanosoma brucei
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RBP10（一种关键的转录后调节因子）在布氏锥虫发育中的作用
DOI：
10.11588/heidok.00023318
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Elisha Mugo
中科院分区：
文献类型：
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作者：
Elisha Mugo
在非洲锥虫中，RNA pol II对转录起始的控制在单个mRNA水平上是不存在的。然而，在生命周期的转变过程中，基因表达会随着宿主环境的变化而发生显著的变化。在哺乳动物宿主的血液中，布氏锥虫以增殖的细长形式或以非分裂的短截形式存在;后者在采采蝇的中肠中分化为原环形式。生命周期各阶段之间的差异基因表达是通过调节mRNA的降解和翻译来实现的，并且主要依赖于RNA结合蛋白。这项工作的重点是RNA结合蛋白RBP 10。RBP 10是一种具有单一RRM结构域的血流形式特异性胞质蛋白。由于发育表达的mRNA的错误调节，血流形式中的RBP 10的耗尽或前循环形式中的强制表达是致命的。在转移到原环生长培养基中并在27 ℃下孵育后，血流形成细胞耗尽RBP 10分化为原环形式;在三天内，>80%的细胞表达GPEET原环素，并重新定位它们的动基体。相反，RBP 10在前循环细胞中表达两天将细胞转化为血流形式。在这样的细胞中，八个VSG转录本，包括三个具有元环启动子的转录本，被强烈上调，并且约16%的细胞获得了VSG表面涂层。更重要的是，一部分细胞在转移到血流形式的生长培养基中并在37 ℃下孵育后存活，导致细胞在约10天内增殖。 RBP 10与报告mRNA的拴系抑制翻译并促进mRNA降解。来自血流形式的RBP 10共沉淀许多在血流形式中通常不稳定的前环特异性mRNA。事实上，RBP 10耗竭后上调的39%的mRNA被其结合;这些包括编码前环表面包衣EP前环素的转录物、前环能量代谢所需的几种酶、调节蛋白ZC 3 H21、ZC 3 H20、两种激酶和一种磷酸酶。发现UA（U）6基序在RBP 10 mRNA靶的3' UTR中高度富集。当UA（U）6基序从报告mRNA中缺失时，RBP 10与EP 3' UTR的结合丧失，并且该基序也是RBP 10对其调控所必需的。在血流形式中，RBP 10靶mRNA可能被阻止翻译，因此降解;这对生存很重要。因此，RBP 10表达的扰动触发了足以调节T.发展能力。
In African trypanosomes, the control of transcription initiation by RNA pol II is absent at the level of individual mRNAs. Nevertheless, gene expression changes dramatically during life cycle transitions in response to the changing host environments. In the bloodstream of the mammalian host, Trypanosoma brucei exist as proliferative long slender forms or as a non-dividing stumpy forms; the latter differentiate to procyclic forms in the midgut of the tsetse fly. Differential gene expression between life cycle stages is achieved through regulation of mRNA degradation and translation, and mainly relies on RNA binding proteins. The work focuses on the RNA binding protein RBP10. RBP10 is a bloodstream form specific cytoplasmic protein with a single RRM domain. Depletion of RBP10 in bloodstream forms or forced expression in the procyclic forms is lethal due to mis-regulation of developmentally expressed mRNAs. Bloodstream forms cells depleted of RBP10 differentiate to procyclic forms after transfer into procyclic growth media and incubation at 27oC; within three days, >80% of the cells express GPEET procyclin, and reposition their kinetoplast. Conversely, expression of RBP10 in procyclic cells for two days converts the cells to bloodstream forms. In such cells, eight VSG transcripts, including three with metacyclic promoters, were strongly up regulated, and ~16% of the cells had acquired a VSG surface coat. More importantly, a subset of the cells survived after transfer into bloodstream form growth media and incubation at 37oC, resulting in proliferating cells in about ten days. Tethering of RBP10 to a reporter mRNA inhibits translation and promotes mRNA degradation. RBP10 from bloodstream forms co-precipitated many procyclic specific mRNAs that are normally unstable in bloodstream forms. Indeed, 39% of the mRNAs up regulated after RBP10 depletion were bound by it; these included the transcript encoding procyclic surface coat EP procyclin, several enzymes needed for procyclic energy metabolism, regulatory proteins ZC3H21, ZC3H20, two kinases and a phosphatase. The UA(U)6 motif was found to be highly enriched in the 3' UTR of RBP10 mRNA targets. Binding of RBP10 to EP 3’ UTR was lost when the UA(U)6 motif was deleted from a reporter mRNA, and the motif was also necessary for its regulation by RBP10. In bloodstream forms RBP10 target mRNAs are likely to be blocked from translation hence degraded; this is important for survival. Perturbation of RBP10 expression therefore triggers a regulatory cascade that is sufficient to modulate T. brucei developmental capacity.