Regulation of mRNA Decapping in Human Cells

mRNA稳定性的调节在控制许多生长因子、细胞因子和转录因子的表达中起关键作用。 因此，受调节的mRNA周转在细胞生长、分化和发育中起着重要作用，并且可以对包括癌症在内的几种疾病状态产生重大影响。 然而，介导调节mRNA周转的机制和因素通常不清楚。我们在哺乳动物细胞中发现了一种新的酶活性，可以特异性地去除mRNA的5'帽。 此外，在我们的体外测定系统中，这种开盖活性受到高度调节。 转录物的poly（A）尾与poly（A）结合蛋白结合，通过一种新的eIF 4 E-独立复合物特异性抑制去帽。 AU丰富的不稳定性元素，调节许多短寿命的mRNA在体内的稳定性，显着刺激脱帽在我们的体外试验。在这个应用程序中，我们将建立在这些观察和研究的基础上，调节哺乳动物细胞中的mRNA去帽的机制。 首先，我们建议确定和表征新的人类去帽酶。 其次，我们将研究poly（A）介导的去帽抑制的机制。 最后，我们将解决的因素和机制参与的刺激开盖富AU不稳定元素。 总之，这些研究应该提供关键的见解，这一重要领域的转录后调节基因表达的哺乳动物细胞。

Regulation of mRNA stability plays a key role in controlling the expression of many growth factors, cytokines and transcription factors. Regulated mRNA turnover, therefore, plays an important role in cell growth, differentiation and development, and can have a significant impact on several disease states, including cancer. The mechanisms and factors that mediate regulated mRNA turnover are, however, generally unclear. We have discovered a novel enzymatic activity in mammalian cells that specifically removes the 5' cap from mRNAs. Furthermore, this decapping activity is highly regulated in our in vitro assay system. The poly (A) tail of the transcript, in conjuction with poly (A) binding protein, specifically represses decapping through a novel, elF4E-independent complex. AU-rich instability elements, which regulate the stability of many short-lived mRNAs in vivo, dramatically stimulate decapping in our in vitro assays. In this application, we will build upon these observations and investigate the underlying mechanisms that regulate decapping of mRNAs in mammalian cells. First, we propose to identify and characterize the novel human decapping enzyme. Second, we will investigate the mechanism of poly(A)-mediated repression of decapping. Finally, we will address the factors and mechanisms involved in the stimulation of decapping by AU-rich instability elements. In total, these studies should provide pivotal insights into this important area of post-transcriptional regulation of gene expression in mammalian cells.