The prefoldin bud27 mediates the assembly of the eukaryotic RNA polymerases in an rpb5-dependent manner.
The prefoldin bud27 mediates the assembly of the eukaryotic RNA polymerases in an rpb5-dependent manner.
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DOI：
10.1371/journal.pgen.1003297
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发表时间：
2013
期刊：
影响因子：
4.5
通讯作者：
Navarro F
中科院分区：
文献类型：
--
作者：
Mirón-García MC;Garrido-Godino AI;García-Molinero V;Hernández-Torres F;Rodríguez-Navarro S;Navarro F
在人类中，非常规的前折叠蛋白URI/RMP及其在酵母中的直向同源物Bud 27已被提出参与RNA聚合酶的生物合成。然而，Bud 27的这一作用尚未得到证实，也没有得到很好的阐明。我们的数据有助于阐明这三种真核RNA pols的生物发生机制。我们的证据表明，Bud 27是第一个例子的蛋白质，参与生物合成的三个真核RNA聚合酶和第一个例子的蛋白质调节其组装，而不是他们的核运输。此外，我们证明了Bud 27在RNA pols生物合成中的作用依赖于Rpb 5。事实上，BUD 27的缺乏影响生长，并导致三种RNA聚合酶在细胞质中大量积累，RPB 5的过表达抵消了缺陷。支持这一点，我们的数据表明，Bud 27的缺乏影响Rpb 5和Rpb 6的三种RNA聚合酶的正确组装，这表明这一过程发生在细胞质中，是核输入之前所需的步骤。此外，我们的数据支持这样的观点，即Rpb 5和Rpb 6组装稍晚于其余的复合物。此外，Bud 27 Rpb 5结合结构域而非PFD结合结构域是RNA聚合酶生物合成所必需的。在协议中，我们还证明了BUD 27，RPB 5和RPB 6之间的遗传相互作用。Bud 27在细胞核和细胞质之间以Xpo 1独立的方式穿梭，并且也独立于微管极化，并且可能独立于其与RNA pols的关联。我们的数据还表明，Bud 27在RNA pols生物合成中的作用是独立的伴侣蛋白前折叠蛋白（PFD）复合物和Iwr 1。最后，URI的作用似乎在人类中是保守的，这表明RNA pols生物合成中的保守机制。三种真核生物RNA聚合酶的组装和转运机制进行了讨论。有趣的论文已经证明了一些蛋白质参与核RNA聚合酶的组装及其向核的运输，但所涉及的机制知之甚少。我们的数据有助于澄清三个真核RNA pols的生物发生的机制，并表明酿酒酵母的prefoldin Bud 27介导的三个复合物的正确组装之前，他们的易位到细胞核，在一个过程中，这是依赖于RPB 5。此外，我们的数据支持这样的观点，即在RNA pols的组装过程中，Rpb 5和Rpb 6的组装比其余的复合物晚。此外，Bud 27的这种作用似乎是特异性的，因为它不延伸到其他前折叠蛋白成员。最后，Bud 27的作用似乎在人类中是保守的，这表明RNA pols生物合成中的保守机制。
The unconventional prefoldin URI/RMP, in humans, and its orthologue in yeast, Bud27, have been proposed to participate in the biogenesis of the RNA polymerases. However, this role of Bud27 has not been confirmed and is poorly elucidated. Our data help clarify the mechanisms governing biogenesis of the three eukaryotic RNA pols. We show evidence that Bud27 is the first example of a protein that participates in the biogenesis of the three eukaryotic RNA polymerases and the first example of a protein modulating their assembly instead of their nuclear transport. In addition we demonstrate that the role of Bud27 in RNA pols biogenesis depends on Rpb5. In fact, lack of BUD27 affects growth and leads to a substantial accumulation of the three RNA polymerases in the cytoplasm, defects offset by the overexpression of RPB5. Supporting this, our data demonstrate that the lack of Bud27 affects the correct assembly of Rpb5 and Rpb6 to the three RNA polymerases, suggesting that this process occurs in the cytoplasm and is a required step prior to nuclear import. Also, our data support the view that Rpb5 and Rpb6 assemble somewhat later than the rest of the complexes. Furthermore, Bud27 Rpb5-binding but not PFD-binding domain is necessary for RNA polymerases biogenesis. In agreement, we also demonstrate genetic interactions between BUD27, RPB5, and RPB6. Bud27 shuttles between the nucleus and the cytoplasm in an Xpo1-independent manner, and also independently of microtubule polarization and possibly independently of its association with the RNA pols. Our data also suggest that the role of Bud27 in RNA pols biogenesis is independent of the chaperone prefoldin (PFD) complex and of Iwr1. Finally, the role of URI seems to be conserved in humans, suggesting conserved mechanisms in RNA pols biogenesis. The mechanisms governing the assembly and the transport of the three eukaryotic RNA polymerases to the nucleus are in discussion. Interesting papers have demonstrated the participation of some proteins in the assembly of the nuclear RNA polymerases and in their transport to the nucleus, but the mechanisms involved are poorly understood. Our data help clarify the mechanisms governing biogenesis of the three eukaryotic RNA pols and demonstrate that the prefoldin Bud27 of Saccharomyces cerevisiae mediates the correct assembly of the three complexes prior to their translocation to the nucleus, in a process which is dependent on Rpb5. In addition, our data support the view that, during the assembly of the RNA pols, Rpb5 and Rpb6 assemble rather late compared to the rest of the complexes. Furthermore, this role of Bud27 seems to be specific, as it is not extended to other prefoldin members. Finally, the role of Bud27 seems to be conserved in humans, suggesting conserved mechanisms in RNA pols biogenesis.
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