Peng S S, Chen C Y, Shyu A B
Department of Biochemistry and Molecular Biology, The University of Texas Houston Health Science Center, 77030, USA.
Mol Cell Biol. 1996 Apr;16(4):1490-9. doi: 10.1128/MCB.16.4.1490.
AU-rich RNA-destabilizing elements (AREs) found in the 3' untranslated regions of many labile mRNAs encoding proto-oncoproteins and cytokines generally contain (i) one or more copies of the AUUUA pentanucleotide and (ii) a high content of uridylate and sometimes also adenylate residues. Recently, we have identified a potent ARE from the 3' untranslated region of c-jun proto-oncogene mRNA that does not contain the AUUUA motif. In an attempt to further our understanding of the general principles underlying mechanisms by which AREs direct rapid and selective mRNA degradation, in this study we have characterized the functionally important structural features and properties of this non-AUUUA ARE. Like AUUUA-containing AREs, this non-AUUUA ARE directs rapid shortening of the poly(A) tail as a necessary first step for mRNA degradation. It can be further dissected into three structurally and functionally distinct regions, designated domains I, II, and III. None of three domains alone is able to significantly destabilize the stable beta-globin mRNA. The two unlinked domains, I and III, together are necessary and sufficient for specifying the full destabilizing function of this non-AUUUA ARE. Domain II appears functionally dispensable but can partially substitute for domain I. Domain swaps made between the c-jun non-AUUUA and the c-fos AUUUA-containing AREs reveal that the two AREs, while sharing no sequence homology, appear to contain sequence domains that are structurally distinct but functionally overlapping and exchangeable. These data support the idea that the ultimate destabilizing function of an individual ARE is determined by its own unique combination of structurally distinct and functionally interdependent domains. Our polysome profile studies show tha the destabilizing function of the c-jun non-AUUUA ARE does not require any active transit by ribosomes of the mRNA bearing it, further corroborating that the destabilizing function of AREs is not tightly coupled to ongoing translation by ribosomes. Moreover, unlike AUUUA-containing AREs, the c-jun ARE is insensitive to blockage of its effects by addition of transcription inhibitors. Thus, our data provide further evidence for the existence of a novel class of ARE with unique properties.
富含AU的RNA不稳定元件（ARE）存在于许多编码原癌蛋白和细胞因子的不稳定mRNA的3'非翻译区，通常包含：（i）AUUUA五核苷酸的一个或多个拷贝；（ii）尿苷酸含量高，有时腺苷酸残基含量也高。最近，我们从c-jun原癌基因mRNA的3'非翻译区鉴定出一个有效的ARE，它不包含AUUUA基序。为了进一步了解ARE指导快速和选择性mRNA降解机制的一般原理，在本研究中，我们对这个非AUUUA ARE的功能重要结构特征和特性进行了表征。与含AUUUA的ARE一样，这个非AUUUA ARE指导多聚腺苷酸尾巴的快速缩短，这是mRNA降解的必要第一步。它可以进一步分为三个结构和功能不同的区域，分别命名为结构域I、II和III。单独的三个结构域都不能显著使稳定的β-珠蛋白mRNA不稳定。两个不相连的结构域I和III一起对于指定这个非AUUUA ARE的完全不稳定功能是必要且充分的。结构域II在功能上似乎是可有可无的，但可以部分替代结构域I。在c-jun非AUUUA和含c-fos AUUUA的ARE之间进行的结构域交换表明，这两个ARE虽然没有序列同源性，但似乎包含结构不同但功能重叠且可交换的序列结构域。这些数据支持这样一种观点，即单个ARE的最终不稳定功能由其结构不同且功能相互依赖的结构域的独特组合决定。我们的多核糖体图谱研究表明，c-jun非AUUUA ARE的不稳定功能不需要携带它 的mRNA的核糖体进行任何主动转运，进一步证实了ARE的不稳定功能与核糖体正在进行的翻译没有紧密联系。此外，与含AUUUA的ARE不同，c-jun ARE对添加转录抑制剂阻断其作用不敏感。因此，我们的数据为存在一类具有独特性质的新型ARE提供了进一步的证据。
