AUUUA IS NOT SUFFICIENT TO PROMOTE POLY(A) SHORTENING AND DEGRADATION OF AN MESSENGER-RNA - THE FUNCTIONAL SEQUENCE WITHIN AU-RICH ELEMENTS MAY BE UUAUUUA(U/A)(U/A)
AUUUA IS NOT SUFFICIENT TO PROMOTE POLY(A) SHORTENING AND DEGRADATION OF AN MESSENGER-RNA - THE FUNCTIONAL SEQUENCE WITHIN AU-RICH ELEMENTS MAY BE UUAUUUA(U/A)(U/A)
复制标题
DOI：
10.1128/mcb.14.12.7984
复制
发表时间：
1994-12-01
影响因子：
5.3
通讯作者：
GOODALL, GJ
中科院分区：
文献类型：
--
作者：
LAGNADO, CA;BROWN, CY;GOODALL, GJ
已经显示在几种细胞因子和癌基因mRNA的3'非翻译区中的富含AU的元件（战神）作为mRNA快速降解的信号起作用，并且假定在3'非翻译区中含有富含AU的序列的许多其他细胞因子和癌基因mRNA类似地靶向快速转换。我们已经使用了一个嵌合基因组成的主要是生长激素序列与c-fos启动子驱动的表达，以调查所需的最小序列作为一个功能性的不稳定元素，并监测这些序列的降解途径中的早期步骤的影响。我们发现，AUUUA、UAUUUA和AUUUAU都不能作为不稳定因素发挥作用。然而，当序列UAUUUAU以三个拷贝存在时，足以使嵌合mRNA不稳定。我们提出，该序列的功能是作为一个足够大的序列，UUAUUUA（U/A）（U/A），我们建议形成一个不稳定因子的最佳结合位点的一部分。去稳定化效应取决于该提议的结合位点的拷贝数及其在前两个和后两个位置的错配程度，AUUUA序列中的错配是不容许的。我们发现ARE对降解速率的影响与对poly（A）缩短速率的影响之间存在严格的相关性，这与去腺苷化是降解中的第一个和限速步骤以及受不稳定战神刺激的步骤一致。观察到脱腺苷酸化发生在至少两个阶段中，其中寡核苷酸（A）中间体瞬时积累，这与酵母和哺乳动物细胞中的降解过程可能相似的建议一致。特别是富含U和不含UUAUUUA（U/A）（U/A）基序的战神，无论是在次优去稳定战神的下游还是单独存在时，都不能影响降解速率或去腺苷化速率。
AU-rich elements (AREs) in the 3' untranslated regions of several cytokine and oncogene mRNAs have been shown to function as signals for rapid mRNA degradation, and it is assumed that the many other cytokine and oncogene mRNAs that contain AU-rich sequences in the 3' untranslated region are similarly targeted for rapid turnover. We have used a chimeric gene composed mostly of growth hormone sequences with expression driven by the c-fos promoter to investigate the minimal sequence required to act as a functional destabilizing element and to monitor the effect of these sequences on early steps in the degradation pathway. We find that neither AUUUA, UAUUUA, nor AUUUAU can function as a destabilizing element. However, the sequence UAUUUAU, when present in three copies, is sufficient to destabilize a chimeric mRNA. We propose that this sequence functions by virtue of being a sufficient portion of the larger sequence, UUAUUUA(U/A)(U/A), that we propose forms the optimal binding site for a destabilizing factor. The destabilizing effect depends on the number of copies of this proposed binding site and their degree of mismatch in the first two and last two positions, with mismatches in the AUUUA sequence not being tolerated. We found a strict correlation between the effect of an ARE on degradation rate and the effect on the rate of poly(A) shortening, consistent with deadenylation being the first and rate-limiting step in degradation, and the step stimulated by destabilizing AREs. Deadenylation was observed to occur in at least two phases, with an oligo(A) intermediate transiently accumulating, consistent with the suggestion that the degradation processes may be similar in yeast and mammalian cells. AREs that are especially U rich and contain no UUAUUUA(U/A)(U/A) motifs failed to influence the degradation rate or the deadenylation rate, either when downstream of suboptimal destabilizing AREs or when alone.