Mechanism for Aar2p function as a U5 snRNP assembly factor.
Mechanism for Aar2p function as a U5 snRNP assembly factor.
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DOI：
10.1101/gad.635911
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发表时间：
2011-08
影响因子：
10.5
通讯作者：
G. Weber;Vanessa F. Cristão;Flavia de L Alves;K. Santos;N. Holton;J. Rappsilber;J. Beggs;M. Wahl
中科院分区：
文献类型：
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作者：
G. Weber;Vanessa F. Cristão;Flavia de L Alves;K. Santos;N. Holton;J. Rappsilber;J. Beggs;M. Wahl
关于颗粒特异性蛋白是如何组装在剪接体小核糖核蛋白(SnRNP)上的，人们知之甚少。Brr2p是剪接体催化激活和拆解所必需的U5 SnRNP特异性RNA解旋酶。在酵母中，Aar2蛋白是细胞质前体U5 SnRNP的一部分，该前体缺乏Brr2p，并在细胞核中被Brr2p取代。在这里，我们发现Aar2p和Brr2p与Prp8p的C-端区的不同结构域结合；Aar2p与RNAseH结构域相互作用，而Brr2p与Jab1/MPN结构域相互作用。这些结构域通过一个长而灵活的连接子连接，但Aar2p-RNAseH复合体隔离了Jab1/MPN结构域，从而阻止了Brr2p的结合。Aar2p在体内被磷酸化，Aar2p中模拟磷酸的S253E突变导致Aar2p-Prp8p复合体的破坏，有利于Brr2p-Prp8p复合体。我们提出了一个模型，其中Aar2p作为磷酸化控制的U5 SnRNP组装因子，调节颗粒特异性Brr2p的掺入。这一调控的目的可能是为了防止非特异性RNA与Prp8p结合和/或Brr2p活性的过早激活。
Little is known about how particle-specific proteins are assembled on spliceosomal small nuclear ribonucleoproteins (snRNPs). Brr2p is a U5 snRNP-specific RNA helicase required for spliceosome catalytic activation and disassembly. In yeast, the Aar2 protein is part of a cytoplasmic precursor U5 snRNP that lacks Brr2p and is replaced by Brr2p in the nucleus. Here we show that Aar2p and Brr2p bind to different domains in the C-terminal region of Prp8p; Aar2p interacts with the RNaseH domain, whereas Brr2p interacts with the Jab1/MPN domain. These domains are connected by a long, flexible linker, but the Aar2p-RNaseH complex sequesters the Jab1/MPN domain, thereby preventing binding by Brr2p. Aar2p is phosphorylated in vivo, and a phospho-mimetic S253E mutation in Aar2p leads to disruption of the Aar2p-Prp8p complex in favor of the Brr2p-Prp8p complex. We propose a model in which Aar2p acts as a phosphorylation-controlled U5 snRNP assembly factor that regulates the incorporation of the particle-specific Brr2p. The purpose of this regulation may be to safeguard against nonspecific RNA binding to Prp8p and/or premature activation of Brr2p activity.