Beutler B, Thompson P, Keyes J, Hagerty K, Crawford D
Howard Hughes Medical Institute, University of Texas Health Science Center, Dallas 75235.
Biochem Biophys Res Commun. 1988 May 16;152(3):973-80. doi: 10.1016/s0006-291x(88)80379-6.
mRNA molecules encoding a number of inflammatory cytokines, as well as certain proto-oncogenes, contain a conserved UA-exclusive sequence in the 3' untranslated region that confers message instability in vivo. This sequence may comprise a critical regulatory element, governing the level of these mRNA molecules, and determining the efficiency with which they are translated. Through the use of a double-label RNAse assay, we have determined that lysates prepared from mouse macrophages selectively degrade mRNA molecules containing the 3' untranslated UA sequence found in the mRNA encoding human cachectin/TNF. The degree of instability is dependent upon the number of copies of inserted UA sequence present in the target mRNA molecule (a Xenopus beta-globin mRNA). mRNAs containing randomly generated UA sequences are more labile than unmodified globin mRNA, but less susceptible to degradation than mRNAs containing the authentic cachectin-derived sequence. mRNA molecules containing synthetic UG-exclusive sequences are normally stable or protected in vitro. The destruction of UA-containing mRNA is inhibited by random adenylate/uridilate copolymers, but not by guanylate/uridilate copolymers. Boiling or proteinase K treatment destroys the selective nucleolytic activity of macrophage lysates. We propose that the nuclease measured here may serve to regulate cellular levels of mRNA molecules encoding cachectin, other inflammatory cytokines, and certain proto-oncogene products.
编码多种炎性细胞因子以及某些原癌基因的信使核糖核酸（mRNA）分子，在其3'非翻译区含有一个保守的仅含UA的序列，该序列在体内赋予信使核糖核酸不稳定性。这个序列可能构成一个关键的调控元件，控制这些mRNA分子的水平，并决定它们的翻译效率。通过使用双标记核糖核酸酶测定法，我们已确定从小鼠巨噬细胞制备的裂解物能选择性地降解含有在编码人恶病质素/肿瘤坏死因子（cachectin/TNF）的mRNA中发现的3'非翻译UA序列的mRNA分子。不稳定性的程度取决于靶mRNA分子（非洲爪蟾β-珠蛋白mRNA）中插入的UA序列的拷贝数。含有随机产生的UA序列的mRNA比未修饰的珠蛋白mRNA更不稳定，但比含有源自天然恶病质素序列的mRNA更不易被降解。含有合成的仅含UG序列的mRNA分子在体外通常是稳定的或受到保护。含UA的mRNA的降解受到随机腺苷酸/尿苷酸共聚物的抑制，但不受鸟苷酸/尿苷酸共聚物的抑制。煮沸或蛋白酶K处理会破坏巨噬细胞裂解物的选择性核酸分解活性。我们提出这里检测到的核酸酶可能用于调节编码恶病质素、其他炎性细胞因子以及某些原癌基因产物的mRNA分子的细胞水平。
