Function of QKI RNA-binding Protein in CNS Myelination

描述（由申请人提供）：积累的证据表明， RNA结合蛋白在细胞功能和发育中起着重要作用。的 本申请的目的是了解RNA结合的功能， 髓鞘形成中的QKT蛋白。髓鞘生成细胞中QKI表达减少 导致quakingviable（qvod）小鼠中严重的髓鞘形成障碍。QKI是 RNA的信号转导激活因子（STARs），它携带一个单一的 RNA结合结构域以及几个Src同源3（SH 3）结合结构域，因此 可以与RNA和信号分子相互作用。星星蛋白， 磷酸化反应的信号级联，被假定发挥 对细胞RNA的调节作用。根据这一观点，我们 发现QKI选择性地与编码髓鞘碱性磷酸酶的mRNA相互作用， 蛋白（MBP），而QK 1的酪氨酸磷酸化显着降低了这一点 互动这种相互作用的功能重要性通过我们的 最近的发现是MBP mRNA严重不稳定和错误定位在 其中QKI几乎完全丢失的ql少突胶质细胞。这些发现 提示MBP mRNA是髓鞘形成中QKI功能性靶点， QKI和MBP mRNA之间的相互作用在控制正常的 MBP mRNA的转录后命运。本申请集中于 描述QKI调节代谢的分子机制， MBP mRNA。提出了三个具体目标：1）确定是否 MBP mRNA的加速降解发生在qkt约/qkt的细胞质中， 少突胶质细胞，以及QKI表达升高是否会延长 MBP mRNA; 2）为了确定MBP mRNA元件与 QKI，并确定该元件是否介导QIU对mRNA的影响 3）为了测试QKI的酪氨酸磷酸化是否调节其稳定性， 结合和稳定mRNA的能力。回答这些问题之前应 大大提高了我们对基本机制的认识， 髓鞘形成，并提供了mRNA代谢是如何 由蛋白质-RNA相互作用控制。这可能最终导致新的 针对髓鞘疾病的治疗策略。此外，了解如何 QKI在髓鞘形成过程中调节其RNA靶点， 其他STAR在细胞生长和肿瘤发生中的作用机制。

DESCRIPTION (provided by applicant): Accumulating evidence suggests that RNA-binding proteins play important roles in cell function and development. The goal of this application is to understand the function of the RNA-binding protein QKT in myelination. Diminished QKI expression in myelin-producing cells leads to severe dysmyelination in quakingviable (qkv) mice. QKI is a member of the Signal Transduction Activators of RNA (STARs), which carries a single RNA-binding domain as well as several Src-Homology 3 (SH3)-binding domains thus can interact with both RNA and signaling molecules. STAR proteins, upon phosphorylation in response to signaling cascades, are postulated to exert regulatory influences on cellular RNAs. Consistent with this view, we have found that QKI selectively interacts with the mRNA encoding the myelin basic protein (MBP), and tyrosine phosphorylation of QK1 dramatically reduces this interaction. The functional importance of this interaction is reinforced by our recent finding that MBP mRNA is severely destabilized and mislocalized in the qkv oligodendrocytes in which QKI is almost completely lost. These findings suggest that MBP mRNA is a functional target for QKI in myelination, and the interaction between QKI and the MBP mRNA is critical in controlling the normal posttranscriptional fate of the MBP mRNA. This application focuses on delineating the molecular mechanisms by which QKI regulates the metabolism of the MBP mRNA. Three specific aims are proposed: 1) To determine whether accelerated degradation of MBP mRNA occurs in the cytoplasm of qkt about/qkv oligodendrocytes, and whether elevated QKI expression prolongs the half-life of the MBP mRNA; 2) To define the MBP mRNA element required for interaction with QKI and to determine whether this element mediates QIU' s effect on mRNA stability; 3) To test whether tyrosine-phosphorylation of QKI regulates its ability to bind and to stabilize mRNA. Answers to these questions should significantly advance our knowledge of fundamental mechanisms governing myelination and provide particular insights into how mRNA metabolism is controlled by protein-RNA interaction. This may ultimately lead to new therapeutic strategies against myelin disorders. In addition, understanding how QKI regulates its RNA targets during myelination may elucidate common mechanisms for other STARs in cell growth and tumorigenesis.