Abstract

Detailed studies of the Gram-negative model bacterium, Escherichia coli, have demonstrated that post-transcriptional events exert important and possibly greater control over gene regulation than transcription initiation or effective translation. Thus, over the past 30 years, considerable effort has been invested in understanding the pathways of mRNA turnover in E. coli. Although it is assumed that most of the ribonucleases and accessory proteins involved in mRNA decay have been identified, our understanding of the regulation of mRNA decay is still incomplete. Furthermore, the vast majority of the studies on mRNA decay have been conducted on exponentially growing cells. Thus, the mechanism of mRNA decay as currently outlined may not accurately reflect what happens when cells find themselves under a variety of stress conditions, such as, nutrient starvation, changes in pH and temperature, as well as a host of others. While the cellular machinery for degradation is relatively constant over a wide range of conditions, intracellular levels of specific ribonucleases can vary depending on the growth conditions. Substrate competition will also modulate ribonucleolytic activity. Post-transcriptional modifications of transcripts by polyadenylating enzymes may favor a specific ribonuclease activity. Interactions with small regulatory RNAs and RNA binding proteins add additional complexities to mRNA functionality and stability. Since many of the ribonucleases are found at the inner membrane, the physical location of a transcript may help determine its half-life. Here we discuss the properties and role of the enzymes involved in mRNA decay as well as the multiple factors that may affect mRNA decay under various in vivo conditions.

摘要

对革兰氏阴性模型细菌大肠杆菌的详细研究表明，转录后事件对基因调控发挥着重要的作用，而且可能比转录起始或有效翻译发挥更大的控制作用。因此，在过去的 30 年中，人们投入了大量精力来了解大肠杆菌中 mRNA 的周转途径. 虽然假设大多数参与 mRNA 衰变的核糖核酸酶和辅助蛋白已被识别，但我们对 mRNA 衰变调控的理解仍然不完整。此外，绝大多数关于 mRNA 衰变的研究都是在呈指数增长的细胞上进行的。因此，目前概述的 mRNA 衰变机制可能无法准确反映当细胞发现自己处于各种压力条件下时会发生什么，例如营养缺乏、pH 值和温度变化以及许多其他条件。虽然降解的细胞机制在广泛的条件下相对恒定，但特定核糖核酸酶的细胞内水平会因生长条件而异。底物竞争也会调节核糖核酸分解活性。聚腺苷酸化酶对转录本的转录后修饰可能有利于特定的核糖核酸酶活性。与小的调节 RNA 和 RNA 结合蛋白的相互作用增加了 mRNA 功能和稳定性的复杂性。由于许多核糖核酸酶在内膜上被发现，转录物的物理位置可能有助于确定其半衰期。在这里，我们讨论了参与 mRNA 衰变的酶的特性和作用，以及在各种条件下可能影响 mRNA 衰变的多种因素。转录物的物理位置可能有助于确定其半衰期。在这里，我们讨论了参与 mRNA 衰变的酶的特性和作用，以及在各种条件下可能影响 mRNA 衰变的多种因素。转录物的物理位置可能有助于确定其半衰期。在这里，我们讨论了参与 mRNA 衰变的酶的特性和作用，以及在各种条件下可能影响 mRNA 衰变的多种因素。体内条件。