Mechanisms of mRNP remodeling in mRNA turnover

描述（由申请人提供）：基因表达可以在多个水平上调节，包括mRNA降解。mRNA的降解速率可以按数量级变化，并且可以由细胞信号调节，从而改变mRNA水平，从而响应于细胞条件的变化而改变蛋白质产生。mRNA与蛋白质复合存在于细胞中，形成信使核糖核蛋白（mRNP）。mRNP复合物的蛋白质控制mRNA活性并保护mRNA免于衰变。靶向mRNA降解涉及RNA降解酶的募集-然而，释放mRNP蛋白以允许mRNA降解酶接近mRNA的机制知之甚少。我们最近发现了一种依赖于蛋白Upf 1的ATP水解的活性，该活性对于分解mRNP以允许靶向称为无义介导的衰变（NMD）的mRNA衰变途径的mRNA降解至关重要。本研究的目的是通过以下具体目标了解mRNP重塑和拆卸在各种人类mRNA衰变途径中的重要性和机制。首先，将测试Upf 1过度磷酸化的能力，Upf 1是NMD途径的一个中心组分，含有其激酶Smg 1的多个磷酸化位点，是否在NMD途径中充当mRNA衰变放大器，通过增强mRNA衰变因子募集，使NMD能够在mRNA衰变因子受限时与其他mRNA衰变途径竞争。其次，将测试Upf 1的ATP酶活性是否对于组蛋白mRNP的重塑至关重要，以允许组蛋白mRNA在细胞周期S期结束时衰减。第三，将测试在由与microRNA复合的RNA诱导沉默复合物（RISC）激活的mRNA降解期间，M0 V10（Upf 1的同源物）的ATP酶活性是否是RNP重塑所需的。与公共卫生的相关性mRNA周转的放松管制与许多人类疾病包括癌症有关。本文所述的研究旨在阐明人类细胞中mRNA降解的基本机制，这将为了解mRNA降解在正常条件下如何调节以及在人类疾病中如何解除调节提供见解。

DESCRIPTION (provided by applicant): Gene expression can be regulated at multiple levels including mRNA degradation. The rate of degradation of mRNAs can vary by orders of magnitude and can be regulated by cellular cues, thus altering mRNA levels and thereby protein production in response to changes in cell conditions. mRNAs exist in cells in complex with proteins, forming the messenger ribonucleoproteins (mRNPs). The proteins of the mRNP complex control mRNA activity and protect the mRNA from decay. The targeting of an mRNA for degradation involves the recruitment of RNA degrading enzymes - however, the mechanism by which proteins of the mRNP are released to allow access for the mRNA decay enzymes to the mRNA is poorly understood. We have recently uncovered an activity dependent on ATP hydrolysis by the protein Upf1 that is critical for disassembling the mRNP to allow for degradation of mRNAs targeted to an mRNA decay pathway called nonsense-mediated decay (NMD). The objective of this research is to understand the importance and mechanism of mRNP remodeling and disassembly in various human mRNA decay pathways, through the following specific aims. First, it will be tested whether the ability to hyperphosphorylate Upf1, a central component of the NMD pathway that contains multiple phosphorylation sites for its kinase Smg1, serves as an mRNA decay amplifier in the NMD pathway that, via enhanced mRNA decay factor recruitment, enables NMD to compete with other mRNA decay pathways when mRNA decay factors are limiting. Second, it will be tested whether the ATPase activity of Upf1 is critical for remodeling of histone mRNPs to allow histone mRNA decay at the end of the cell cycle S-phase. Third, it will be tested whether ATPase activity of MOV10, a homolog of Upf1, is required for RNP remodeling during mRNA degradation activated by the RNA induced silencing complex (RISC) in complex with microRNAs. Relevance to Public Health Deregulation of mRNA turnover has been associated with a number of human disorders including cancers. The studies described here are aimed at elucidating fundamental mechanisms underlying the degradation of mRNA in human cells, which should provide insights into how mRNA decay is regulated under normal conditions and deregulated in human disorders.