The Drosophila U2 snRNP protein U2A′ has an essential function that is SNF/U2B" independent
The Drosophila U2 snRNP protein U2A′ has an essential function that is SNF/U2B" independent
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DOI：
10.1093/nar/29.18.3841
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发表时间：
2001-09-15
影响因子：
14.9
通讯作者：
Salz, HK
中科院分区：
文献类型：
--
作者：
Nagengast, AA;Salz, HK
将U2 snRNP募集到前体mRNA是剪接体组装的重要步骤。虽然已经鉴定了U2 snRNP的蛋白质组分，但它们对功能的单独贡献还不清楚。果蝇和人类蛋白质的体外研究表明，两种U2 snRNP特异性蛋白质U2 A '和U2“仅作为二聚体发挥作用。在果蝇中，U2 snRNP中U2 B“对应物Sans-Fille（SNF）的存在对于生存力是不确定的，表明SNF对于U2 snRNP体内功能不是必需的。随着果蝇基因组中一个U2 A '样蛋白的鉴定，我们现在可以在体内研究SNF与其假定的结合伴侣之间的关系。在这里，我们表明，果蝇U2 A '蛋白与SNF在体内相互作用，像它的人类对应物，是U2 snRNP特异性。然而，出乎意料的是，我们发现功能丧失导致致死性，这表明U2 A '而不是SNF对于U2 snRNP功能是关键的。此外，虽然我们证明了SNF蛋白中的几个结构域对于与果蝇U2 A '蛋白的相互作用是重要的，包括在通常的SNF C-末端的冗余结构域，但是我们发现U2 A'不需要异二聚体的形成来实现其重要功能或U2 snRNP组装。因此，这些数据共同证明，在果蝇中，U2 A '具有与其作为SNF/U2 B“的伴侣蛋白的作用无关的基本功能。
Recruitment of the U2 snRNP to the pre-mRNA is an essential step in spliceosome assembly. Although the protein components of the U2 snRNP have been identified, their individual contributions to function are poorly defined. In vitro studies with the Drosophila and human proteins suggest that two of the U2 snRNP-specific proteins, U2A ' and U2 ", function exclusively as a dimer. In Drosophila the presence of the U2B " counterpart, Sans-Fille (SNF), in the U2 snRNP is dispensable for viability, suggesting that SNF is not necessary for U2 snRNP function in vivo. With the identification of a single U2A ' -Iike protein in the Drosophila genome, we can now investigate the relationship between SNF and its putative binding partner in vivo. Here we show that Drosophila U2A ' protein interacts with SNF in vivo and, like its human counterpart, is U2 snRNP specific. Unexpectedly, however, we find that loss of function causes lethality, suggesting that U2A ', but not SNF, is critical for U2 snRNP function. Moreover, although we demonstrate that several domains in the SNF protein are important for the interaction with the Drosophila U2A ' protein, including a redundant domain at the normally dispensable C-terminus, we find that U2A' does not require heterodimer formation for either its vital function or U2 snRNP assembly. Thus together these data demonstrate that in Drosophila U2A' has an essential function that is unrelated to its role as the partner protein of SNF/U2B ".