de Sousa Abreu Raquel, Sanchez-Diaz Patricia C, Vogel Christine, Burns Suzanne C, Ko Daijin, Burton Tarea L, Vo Dat T, Chennasamudaram Soudhamini, Le Shu-Yun, Shapiro Bruce A, Penalva Luiz O F
Children's Cancer Research Institute, University of Texas Health Science Center at San Antonio, Department of Cellular and Structural Biology, San Antonio, TX 78229-390, USA.
J Biol Chem. 2009 May 1;284(18):12125-35. doi: 10.1074/jbc.M809605200. Epub 2009 Mar 3.
Musashi1 (Msi1) is a highly conserved RNA-binding protein with pivotal functions in stem cell maintenance, nervous system development, and tumorigenesis. Despite its importance, only three direct mRNA targets have been characterized so far: m-numb, CDKN1A, and c-mos. Msi1 has been shown to affect their translation by binding to short elements located in the 3'-untranslated region. To better understand Msi1 functions, we initially performed an RIP-Chip analysis in HEK293T cells; this method consists of isolation of specific RNA-protein complexes followed by identification of the RNA component via microarrays. A group of 64 mRNAs was found to be enriched in the Msi1-associated population compared with controls. These genes belong to two main functional categories pertinent to tumorigenesis: 1) cell cycle, cell proliferation, cell differentiation, and apoptosis and 2) protein modification (including ubiquitination and ubiquitin cycle). To corroborate our findings, we examined the impact of Msi1 expression on both mRNA (transcriptomic) and protein (proteomic) expression levels. Genes whose mRNA levels were affected by Msi1 expression have a Gene Ontology distribution similar to RIP-Chip results, reinforcing Msi1 participation in cancer-related processes. The proteomics study revealed that Msi1 can have either positive or negative effects on gene expression of its direct targets. In summary, our results indicate that Msi1 affects a network of genes and could function as a master regulator during development and tumor formation.
Musashi1（Msi1）是一种高度保守的RNA结合蛋白，在干细胞维持、神经系统发育和肿瘤发生中具有关键作用。尽管其很重要，但迄今为止仅鉴定出三个直接的mRNA靶点：m-numb、CDKN1A和c-mos。已表明Msi1通过与位于3'-非翻译区的短元件结合来影响它们的翻译。为了更好地理解Msi1的功能，我们最初在HEK293T细胞中进行了RIP-Chip分析；该方法包括分离特定的RNA-蛋白质复合物，然后通过微阵列鉴定RNA成分。与对照相比，发现一组64种mRNA在与Msi1相关的群体中富集。这些基因属于与肿瘤发生相关的两个主要功能类别：1）细胞周期、细胞增殖、细胞分化和凋亡；2）蛋白质修饰（包括泛素化和泛素循环）。为了证实我们的发现，我们研究了Msi1表达对mRNA（转录组学）和蛋白质（蛋白质组学）表达水平的影响。其mRNA水平受Msi1表达影响的基因具有与RIP-Chip结果相似的基因本体分布，这加强了Msi1参与癌症相关过程。蛋白质组学研究表明，Msi1对其直接靶点的基因表达可产生正向或负向影响。总之，我们的结果表明Msi1影响一个基因网络，并且在发育和肿瘤形成过程中可能作为一个主要调节因子发挥作用。
