Proteasome-mediated proteolysis of SRSF5 splicing factor intriguingly co-occurs with SRSF5 mRNA upregulation during late erythroid differentiation.
Proteasome-mediated proteolysis of SRSF5 splicing factor intriguingly co-occurs with SRSF5 mRNA upregulation during late erythroid differentiation.
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DOI：
10.1371/journal.pone.0059137
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Baklouti F
中科院分区：
文献类型：
--
作者：
Breig O;Baklouti F
SR蛋白具有多种功能，从组成剪接和选择性剪接到mRNA代谢的几乎所有方面。这些发现吸引了越来越多的兴趣来破译控制这些SR蛋白的组织特异性表达的调节机制。在这项研究中，我们发现SRSF5蛋白在红细胞分化过程中急剧下降，与SRSF5 mRNA水平的上调形成对比。蛋白酶体化学抑制提供了强有力的证据，表明内源性SRSF5蛋白以及稳定转染的SRSF5 cDNA衍生的蛋白在细胞进行终末分化时都是蛋白水解的目标。与此一致，功能实验表明，由于蛋白酶体介导的内源性和转染源性SRSF5的靶向作用，SRSF5的过表达增强了增殖细胞中特定的内源性前mrna剪接事件，而在分化细胞中则没有。对SRSF5结构与其翻译后调控和功能之间关系的进一步研究表明，SRSF5的RNA识别基序足以激活mrna前剪接，而蛋白酶体介导的SRSF5蛋白水解需要蛋白c端RS结构域的存在。SR蛋白的磷酸化是促进其活性和亚细胞可利用性的关键翻译后调控。我们在这里表明，抑制cdc2样激酶（CLK）家族和SRSF5上AKT磷酸化位点Ser86的突变对SRSF5的稳定性没有影响。我们推断，至少AKT和CLK信号通路不参与蛋白酶体诱导的红系发育晚期SRSF5的转换。
SR proteins exhibit diverse functions ranging from their role in constitutive and alternative splicing, to virtually all aspects of mRNA metabolism. These findings have attracted growing interest in deciphering the regulatory mechanisms that control the tissue-specific expression of these SR proteins. In this study, we show that SRSF5 protein decreases drastically during erythroid cell differentiation, contrasting with a concomitant upregulation of SRSF5 mRNA level. Proteasome chemical inhibition provided strong evidence that endogenous SRSF5 protein, as well as protein deriving from stably transfected SRSF5 cDNA, are both targeted to proteolysis as the cells undergo terminal differentiation. Consistently, functional experiments show that overexpression of SRSF5 enhances a specific endogenous pre-mRNA splicing event in proliferating cells, but not in differentiating cells, due to proteasome-mediated targeting of both endogenous and transfection-derived SRSF5. Further investigation of the relationship between SRSF5 structure and its post-translation regulation and function, suggested that the RNA recognition motifs of SRSF5 are sufficient to activate pre-mRNA splicing, whereas proteasome-mediated proteolysis of SRSF5 requires the presence of the C-terminal RS domain of the protein. Phosphorylation of SR proteins is a key post-translation regulation that promotes their activity and subcellular availability. We here show that inhibition of the CDC2-like kinase (CLK) family and mutation of the AKT phosphorylation site Ser86 on SRSF5, have no effect on SRSF5 stability. We reasoned that at least AKT and CLK signaling pathways are not involved in proteasome-induced turnover of SRSF5 during late erythroid development.
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