APE1 as a Novel Mammalian Endoribonuclease

生命系统中最基本的活动之一是将它们的遗传信息(DNA)复制到蛋白质中，蛋白质是执行维持有机体存活的大部分生物功能的分子机器。将DNA复制到蛋白质中分两步进行：第一步，将DNA复制到信使核糖核酸(信使核糖核酸，化学上类似于DNA)中；第二步，将信使核糖核酸用作制造特定蛋白质的模板。因此，蛋白质的数量取决于mRNAs的数量。由于信使核糖核酸丰度的变化而导致的许多蛋白质的过剩或不足可能导致疾病，如癌症。MRNAs的丰度在很大程度上取决于其降解的速度。因此，了解mRNA降解机制是如何工作的，对于增加我们对分子生物学的基本科学知识以及揭示一些人类疾病的发病机制是重要的。 人们普遍认为哺乳动物的mRNAs主要是从分子末端降解而来的。然而，最近的几份报告，包括我们自己实验室的一份出版物，开始挑战这一观点。这些报告表明，mRNAs也可以通过分子中间的裂解-这一过程被称为内切核裂解-降解。启动内切核酸酶的酶称为内切核糖核酸酶。我们的实验室最近确定APE1是一种内切核糖核酸酶，它能在试管中裂解c-myc mRNA。我们还发现APE1可以影响细胞中c-myc mRNA的丰度和寿命。我们提出的研究目的是确定APE1在细胞中的RNA靶标，并确定它是否是控制各种RNA分子丰度的重要内切核酸酶。这些研究产生的结果具有很高的潜力来促进我们对基因表达的了解，以及可能导致在RNA降解技术中使用这种酶或其性质。

One of the most fundamental activities in living systems is to copy their genetic information (DNA) into proteins, the molecular machines that carry out most of the biological functions that keep an organism alive. The copying of DNA into proteins occurs in two steps: first, DNA is copied into mRNA (messenger ribonucleic acid; chemically similar to DNA); second, mRNA is used as a template to make specific proteins. The amount of proteins is therefore dependent on the amount of mRNAs. An excess or shortage of many proteins due to changes in the abundance of mRNA can lead to diseases, such as cancer. The abundance of mRNAs is highly dependent on the rate of its degradation. An understanding of how the mRNA degradation machinery works is therefore important for increasing our basic scientific knowledge of molecular biology, as well as for revealing information on the pathogenesis of some human diseases. It has been widely believed that mammalian mRNAs are primarily degraded from the ends of the molecules. However several recent reports including a publication from our own laboratory are beginning to challenge this view. These report have shown that mRNAs can also be degraded through cleavage in the middle of the molecules - a process known as endonucleolytic cleavage. Enzymes that initiate endonucleolytic cleavage are called endoribonucleases. Our laboratory has recently identified APE1 as an endoribonuclease that cleaves c-myc mRNA in a test tube. We have also shown that APE1 can influence the abundance and longevity of c-myc mRNA in cells. The goals of our proposed research are to determine the RNA targets of APE1 in cells, and to ascertain whether it is an important endoribonuclease for controlling the abundance of various RNA molecules. Results generated from these studies have high potential to advance our knowledge of gene expression, as well as possibly leading to the use of the enzyme or its properties in RNA degradation technology.