Regulation of mRNA Decapping in Human Cells

MRNA稳定性的调控在许多生长因子、细胞因子和转录因子的表达调控中起着关键作用。因此，受调控的mRNA周转在细胞的生长、分化和发育中起着重要作用，并可能对包括癌症在内的几种疾病状态产生重大影响。然而，调节调节的信使核糖核酸周转的机制和因素通常还不清楚。我们在哺乳动物细胞中发现了一种新的酶活性，它能特异性地去除mRNAs的5‘端。此外，在我们的体外检测系统中，这种去核糖核酸活性受到高度调控。转录本的聚(A)尾与聚(A)结合蛋白结合，通过一种新的非依赖于elF4E的复合体特异性地抑制解链。富含Au的不稳定元素，在体内调节许多短暂的mRNAs的稳定性，在我们的体外分析中极大地刺激去掉。在这一应用中，我们将在这些观察的基础上，研究调控哺乳动物细胞中mRNAs去掉的潜在机制。首先，我们提出了一种新的人类解离酶的鉴定和性质。其次，我们将研究Poly(A)介导的对去顶抑制的机制。最后，我们将讨论富含Au的不稳定元素刺激拆解的因素和机制。总而言之，这些研究应该为哺乳动物细胞中基因表达的转录后调控这一重要领域提供关键的见解。

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.