Multiple properties of the splicing repressor SRp38 distinguish it from typical SR proteins
Multiple properties of the splicing repressor SRp38 distinguish it from typical SR proteins
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DOI：
10.1128/mcb.25.18.8334-8343.2005
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发表时间：
2005-09-01
影响因子：
5.3
通讯作者：
Manley, JL
中科院分区：
文献类型：
--
作者：
Shin, C;Kleiman, FE;Manley, JL
SR蛋白SRp 38是一种通用的剪接阻遏物，其在有丝分裂期间和响应于热休克通过去磷酸化而被激活。在这里，我们描述的实验，提供洞察机制SRp 38剪接抑制功能。我们首先表明，SRp 38重新分配和共定位与snRNP，但不是一个典型的SR蛋白，SC 35，在有丝分裂和热休克后。支持这种关联的功能意义，微球菌核酸酶敏感组分，即，一个snRNP（s）在体外完全拯救了热休克诱导的剪接抑制，而纯化的U1 snRNP部分地拯救了热休克诱导的剪接抑制。SRp 38含有一个N-末端RNA结合结构域（RBD）和一个C-末端RS结构域，RS结构域由两个亚结构域（RS 1和RS 2结构域）组成。出乎意料的是，RS 1缺失突变体衍生物特异性抑制剪接的第二步，而RS 2缺失突变体保留显着的去磷酸化依赖性抑制活性。使用嵌合SRp 38/SC 35蛋白，我们表明，SC 35-RBD/SRp 38-RS可以作为一个通用的剪接激活剂和去磷酸化的版本可以作为一个强大的剪接阻遏物。然而，SRp 38-RBD/SC 35-RS在这些测定中基本上无活性。总之，我们的研究结果有助于定义SRp 38的不寻常的功能，使其与其他SR蛋白质区分开来。
The SR protein SRp38 is a general splicing repressor that is activated by dephosphorylation during mitosis and in response to heat shock. Here we describe experiments that provide insights into the mechanism by which SRp38 functions in splicing repression. We first show that SRp38 redistributes and colocalizes with snRNPs, but not with a typical SR protein, SC35, during mitosis and following heat shock. Supporting the functional significance of this association, a micrococcal nuclease-sensitive component, i.e., an snRNP(s), completely rescued heat shock-induced splicing repression in vitro, and purified U1 snRNP did so partially. SRp38 contains an N-terminal RNA binding domain (RBD) and a C-terminal RS domain composed of two subdomains (RS1 and RS2 domains). Unexpectedly, an RS1 deletion mutant derivative specifically inhibited the second step of splicing, while an RS2 deletion mutant retained significant dephosphorylation-dependent repression activity. Using chimeric SRp38/SC35 proteins, we show that SC35-RBD/SRp38-RS can function as a general splicing activator and that the dephosphorylated version can act as a strong splicing repressor. SRp38-RBD/SC35-RS, however, was essentially inactive in these assays. Together, our results help to define the unusual features of SRp38 that distinguish it from other SR proteins.