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首页> 外文期刊>Biochimica et Biophysica Acta. Gene Regulatory Mechanisms >Polynucleotide phosphorylase and the archaeal exosome as poly(A)-polymerases
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Polynucleotide phosphorylase and the archaeal exosome as poly(A)-polymerases

机译：多核苷酸磷酸化酶和古细菌外来体为聚（A）-聚合酶

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摘要

The addition of poly(A)-tails to RNA is a phenomenon common to almost all organisms. Not only homopolymeric poly(A)-tails, comprised exclusively of adenosines, but also heteropolymeric poly(A)-rich extensions, which include the other three nucleotides as well, have been observed in bacteria, archaea, chloroplasts, and human cells. Polynucleotide phosphorylase (PNPase) and the archaeal exosome, which bear strong similarities to one another, both functionally and structurally, were found to polymerize the heteropolymeric tails in bacteria, spinach chloroplasts, and archaea. As phosphorylases, these enzymes use diphosphate nucleotides as substrates and can reversibly polymerize or degrade RNA, depending on the relative concentrations of nucleotides and inorganic phosphate. A possible scenario, illustrating the evolution of RNA polyadenylation and its related functions, is presented, in which PNPase (or the archaeal exosome) was the first polyadenylating enzyme to evolve and the heteropolymeric tails that it produced, functioned in a polyadenylation-stimulated RNA degradation pathway. Only at a later stage in evolution, did the poly(A)-polymerases that use only ATP as a substrate, hence producing homopolymeric adenosine extensions, arise. Following the appearance of homopolymeric tails, a new role for polyadenylation evolved; RNA stability. This was accomplished by utilizing stable poly(A)-tails associated with the mature 3' ends of transcripts. Today, stable polyadenylation coexists with unstable heteropolymeric and homopolymeric tails. Therefore, the heteropolymeric poly(A)-rich tails, observed in bacteria, organelles, archaea, and human cells, represent an ancestral stage in the evolution of polyadenylation.
机译：在RNA中添加poly（A）尾巴是几乎所有生物都普遍存在的现象。在细菌，古细菌，叶绿体和人类细胞中不仅观察到不仅仅由腺苷组成的均聚物聚（A）尾巴，而且还包含其他三个核苷酸的富含异聚体聚（A）的延伸。多核苷酸磷酸化酶（PNPase）和古细菌外泌体在功能和结构上都具有很强的相似性，被发现可以聚合细菌，菠菜叶绿体和古细菌中的异质尾巴。作为磷酸化酶，这些酶使用二磷酸核苷酸作为底物，并可以可逆地聚合或降解RNA，具体取决于核苷酸和无机磷酸盐的相对浓度。提出了一个可能的情况，说明了RNA聚腺苷酸化的发展及其相关功能，其中PNPase（或古细菌外来体）是第一个进化的聚腺苷酸化酶，其产生的杂聚尾巴在聚腺苷酸化刺激的RNA降解中起作用途径。仅在进化的后期，才出现仅使用ATP作为底物从而产生均聚物腺苷延伸的多聚（A）聚合酶。均聚物尾巴的出现之后，聚腺苷酸化的新作用得以发展。 RNA稳定性。这是通过利用与转录本成熟的3'末端相关的稳定的poly（A）-tails实现的。如今，稳定的聚腺苷酸化与不稳定的杂聚物和均聚物尾巴共存。因此，在细菌，细胞器，古细菌和人类细胞中观察到的富含多聚聚（A）的尾巴代表了聚腺苷酸化过程的祖先阶段。

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