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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >RNA polymerase Ⅱ-dependent transcription in trypanosomes is associated with a SNAP complex-like transcription factor
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RNA polymerase Ⅱ-dependent transcription in trypanosomes is associated with a SNAP complex-like transcription factor

机译：锥虫中RNA聚合酶Ⅱ依赖性转录与SNAP复合物样转录因子相关

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摘要

Spliced leader RNA transcription is essential for cell viability in trypanosomes. The SL RNA genes are expressed from the only defined RNA polymerase ll-dependent promoter identified to date in the trypanosome genome. The SL RNA gene promoter has been shown by in vitro and in vivo analyses to have a tripartite architecture. The upstream most cis-acting element, called PBP-1E, is located between 70 and 60 bp upstream from the transcription start site. This essential element functions along with two downstream elements to direct efficient and proper initiation of transcription. Electrophoretic mobility-shift studies detected a 122-kDa protein, called PBP-1, which interacts with PBP-1E. This protein is the first sequence-specific, double-stranded DNA-binding protein isolated in trypanosomes. Three polypeptides copurify with PBP-1 activity, suggesting that PBP-1 is composed of 57-, 46-, and 36-kDa subunits. We have cloned the genes that encode the 57- and 46-kDa subunits. The 46-kDa protein is a previously uncharacterized protein and may be unique to trypanosomes. Its predicted tertiary structure suggests it binds DNA as part of a complex. The 57-kDa subunit is orthologous to the human small nuclear RNA-activating protein (SNAP)50, which is an essential subunit of the SNAP complex (SNAPc). In human cells, SNAPc binds to the proximal sequence element in both RNA polymerase Ⅱ- and Ⅲ-dependent small nuclear RNA gene promoters. These findings identify a surprising link in the transcriptional machinery across a large evolutionary distance in the regulation of small nuclear RNA genes in eukaryotes.
机译：剪接的前导RNA转录对于锥虫体内的细胞活力至关重要。 SL RNA基因是从迄今为止在锥虫体基因组中鉴定出的唯一定义的RNA聚合酶ll依赖性启动子表达的。 SL RNA基因启动子已通过体外和体内分析显示具有三重结构。最上游的顺式作用元件称为PBP-1E，​​位于转录起始位点上游70到60 bp之间。该基本元件与两个下游元件一起起作用，以指导有效和适当的转录起始。电泳迁移率变化研究检测到一种称为PBP-1的122 kDa蛋白，该蛋白与PBP-1E相互作用。该蛋白是在锥虫中分离出的第一个序列特异性双链DNA结合蛋白。三种多肽共纯化具有PBP-1活性，表明PBP-1由57-，k-和36-kDa亚基组成。我们已经克隆了编码57 kDa和46 kDa亚基的基因。 46 kDa蛋白是以前未鉴定的蛋白，对于锥虫可能是唯一的。其预测的三级结构表明它结合DNA作为复合物的一部分。 57 kDa亚基与人类小核RNA活化蛋白（SNAP）50直系同源，后者是SNAP复合物（SNAPc）的重要亚基。在人类细胞中，SNAPc与RNA聚合酶Ⅱ和Ⅲ依赖性小核RNA基因启动子中的近端序列元件结合。这些发现确定了在真核生物中小核RNA基因调控中跨较大进化距离的转录机制中令人惊讶的联系。

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