Drosophila SPF45: a bifunctional protein with roles in both splicing and DNA repair.
Drosophila SPF45: a bifunctional protein with roles in both splicing and DNA repair.
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DOI：
10.1371/journal.pgen.0020178
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发表时间：
2006-12-08
期刊：
影响因子：
4.5
通讯作者：
Salz HK
中科院分区：
文献类型：
--
作者：
Chaouki AS;Salz HK
SPF45蛋白的序列非常保守，然而功能研究已经确定它在动物细胞中是一种剪接因子，在植物中是一种DNA修复蛋白。使用遗传和生化相结合的方法来研究这种明显的功能差异，我们统一并验证了这两项研究，证明了果蝇黑腹蛋白是双功能的，在DNA修复和剪接中具有独立的功能。我们发现SPF45与U2 SnRNP相关，移除蛋白质C-末端的突变破坏了这种相互作用。虽然携带这种突变的动物是存活的，但它们在调节性致死剪接的能力上受到了损害，这表明性致死是SPF45的一个重要生理靶点。此外，这些突变的动物表现出难以从外源性诱导的DNA损伤中恢复的表型诊断。通过发现SPF45和RAD201之间的遗传和物理相互作用，SPF45在DNA修复途径中的作用得到了加强。RAD201是RecA/RAD51蛋白家族中一个以前未被描述的成员。再加上我们的发现，苍蝇SPF45蛋白提高了缺乏RecG解旋酶的诱变剂处理的细菌的存活率，这些研究提供了诱人的建议，即SPF45在DNA修复中具有古老的和进化上保守的作用。赋予蛋白质功能依赖于关于不同物种中相似蛋白质的信息，并且基于这样的观点，即序列的保守通常与功能的保守平行。在这篇文章中，Chaouki和Salz将重点放在SPF45上，这种蛋白质乍一看似乎打破了这一规则。虽然SPF45的序列高度保守，但在动物细胞中，SPF45作为剪接因子发挥作用，但在植物细胞中，它作为DNA修复蛋白发挥作用。这种功能的差异在这里通过证明，在黑腹毛虫中，SPF45是一种双功能蛋白质，在DNA修复和剪接中具有独立的功能。对这一结论的支持包括观察到缺乏SPF45功能的突变动物在剪接和DNA修复方面都存在缺陷。此外，作者还表明，SPF45与两组不同的蛋白质有关；那些参与RNA剪接的蛋白质和那些参与DNA修复的蛋白质。黑腹果蝇蛋白质具有双功能的发现表明，人类蛋白质也可能具有多种功能。这具有重要的临床意义，因为SPF45水平升高与化疗耐药有关。
The sequence of the SPF45 protein is significantly conserved, yet functional studies have identified it as a splicing factor in animal cells and as a DNA-repair protein in plants. Using a combined genetic and biochemical approach to investigate this apparent functional discrepancy, we unify and validate both of these studies by demonstrating that the Drosophila melanogaster protein is bifunctional, with independent functions in DNA repair and splicing. We find that SPF45 associates with the U2 snRNP and that mutations that remove the C-terminal end of the protein disrupt this interaction. Although animals carrying this mutation are viable, they are nevertheless compromised in their ability to regulate Sex-lethal splicing, demonstrating that Sex-lethal is an important physiological target of SPF45. Furthermore, these mutant animals exhibit phenotypes diagnostic of difficulties in recovering from exogenously induced DNA damage. The conclusion that SPF45 functions in the DNA-repair pathway is strengthened by finding both genetic and physical interactions between SPF45 and RAD201, a previously uncharacterized member of the RecA/Rad51 protein family. Together with our finding that the fly SPF45 protein increases the survival rate of mutagen-treated bacteria lacking the RecG helicase, these studies provide the tantalizing suggestion that SPF45 has an ancient and evolutionarily conserved role in DNA repair. Assigning function to a protein relies on information about similar proteins in different species, and is based on the view that conservation of sequence generally parallels conservation of function. In this article, Chaouki and Salz focus on SPF45, a protein that, at first glance, appears to break this rule. Although the sequence of SPF45 is highly conserved, in animals cells SPF45 functions as a splicing factor, but in plant cells it functions as a DNA repair protein. This functional discrepancy is resolved here through the demonstration that, in D. melanogaster, SPF45 is a bifunctional protein with independent functions in DNA repair and splicing. Support for this conclusion includes the observation that mutant animals lacking SPF45 function display defects in both splicing and DNA repair. In addition, the authors show that SPF45 associates with two distinct groups of proteins; those that participate in RNA splicing and those that participate in DNA repair. The finding that the D. melanogaster protein is bifunctional suggests that the human protein may also have more than one function. This has important clinical implications because elevated SPF45 levels have been correlated with resistance to chemotherapy.
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