Mechanisms of mRNP remodeling in mRNA turnover

描述(申请人提供)：基因表达可以在多个水平上进行调节，包括mRNA降解。MRNAs的降解速度可以按数量级变化，并可以受到细胞信号的调节，从而改变mRNAs的水平，从而对细胞条件的变化做出反应，从而产生蛋白质。MRNAs以蛋白质复合体形式存在于细胞内，形成信使核糖核蛋白(MRNPs)。MRNP复合体的蛋白质控制信使核糖核酸的活性，保护信使核糖核酸免于腐烂。将mRNA作为降解的靶点涉及RNA降解酶的招募--然而，人们对mRNP的蛋白质被释放以使mRNA衰变酶能够接触到mRNA的机制知之甚少。我们最近发现了一种依赖于蛋白质UPF1的ATP水解的活性，这对于分解mRNP以便允许降解针对被称为无义介导的衰退(NMD)的mRNA衰退途径的mRNAs是至关重要的。本研究的目的是通过以下具体目的来了解mRNP重塑和分解在不同的人类mRNA衰变途径中的重要性和机制。首先，将测试UPF1过度磷酸化的能力，UPF1是NMD途径的一个中心组成部分，包含其激酶SMG1的多个磷酸化位点，是否在NMD途径中作为mRNA衰减放大器，通过增强的mRNA衰减因子募集，使NMD在mRNA衰减因子有限的情况下与其他mRNA衰减途径竞争。其次，将测试UPF1的ATPase活性是否是组蛋白mRNPs重塑的关键，从而允许组蛋白mRNA在细胞周期结束时衰退--S期。第三，将测试UPF1的同源物MOV10的ATPase活性是否需要在RNA诱导沉默复合体(RISC)与microRNAs的复合物激活的mRNA降解过程中RNP的重塑。与公共卫生的相关性放松信使核糖核酸的周转与包括癌症在内的许多人类疾病有关。本文描述的研究旨在阐明人类细胞中信使核糖核酸降解的基本机制，这应该为在正常条件下调节信使核糖核酸的衰变以及在人类疾病中如何解除对信使核糖核酸的调节提供见解。

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.