Curatola A M, Nadal M S, Schneider R J
Department of Biochemistry, New York University Medical Center, New York 10016, USA.
Mol Cell Biol. 1995 Nov;15(11):6331-40. doi: 10.1128/MCB.15.11.6331.
The 3' noncoding region (NCR) AU-rich element (ARE) selectively confers rapid degradation on many mRNAs via a process requiring translation of the message. The role of cotranslation in destabilization of ARE mRNAs was examined by insertion of translation-blocking stable secondary structure at different sites in test mRNAs containing either the granulocyte-macrophage colony-stimulating factor (GM-CSF) ARE or a control sequence. A strong (-80 kcal/mol [1 kcal = 4.184 kJ]) but not a moderate (-30 kcal/mol) secondary structure prevented destabilization of mRNAs when inserted at any position upstream of the ARE, including in the 3' NCR. Surprisingly, a strong secondary structure did not block rapid mRNA decay when placed immediately downstream of the ARE. Studies are also presented showing that the turnover of mRNAs containing control or ARE sequences is not altered by insertion of long (1,000-nucleotide) intervening segments between the stop codon and the ARE or between the ARE and poly(A) tail. Characterization of ARE-containing mRNAs in polyadenylated and whole cytoplasmic RNA fractions failed to find evidence for decay intermediates degraded to the site of strong secondary structure from either the 5' or 3' end. From these and other data presented, this study demonstrates that complete translation of the coding region is essential for activation of rapid mRNA decay controlled by the GM-CSF ARE and that the structure of the 3' NCR can strongly influence activation. The results are consistent with activation of ARE-mediated decay by possible entry of translation-linked decay factors into the 3' NCR or translation-coupled changes in 3' NCR ribonucleoprotein structure or composition.
3'非编码区（NCR）富含AU元件（ARE）通过一种需要对信息进行翻译的过程，选择性地使许多mRNA快速降解。通过在含有粒细胞-巨噬细胞集落刺激因子（GM-CSF）ARE或对照序列的测试mRNA的不同位点插入翻译阻断性稳定二级结构，研究了共翻译在ARE mRNA不稳定化中的作用。当在ARE上游的任何位置（包括3' NCR）插入时，强二级结构（-80千卡/摩尔[1千卡 = 4.184千焦]）而非中等强度的二级结构（-30千卡/摩尔）可阻止mRNA的不稳定化。令人惊讶的是，当强二级结构紧邻ARE下游放置时，并不会阻断mRNA的快速降解。研究还表明，在终止密码子与ARE之间或ARE与聚腺苷酸（poly(A)）尾之间插入长的（1000个核苷酸）间隔片段，不会改变含有对照或ARE序列的mRNA的周转。对聚腺苷酸化和全细胞质RNA组分中含ARE的mRNA进行表征，未发现有证据表明存在从5'端或3'端降解至强二级结构位点的衰变中间体。基于这些及其他所呈现的数据，本研究表明编码区的完整翻译对于由GM-CSF ARE控制的快速mRNA降解的激活至关重要，并且3' NCR的结构可强烈影响激活过程。这些结果与通过翻译相关的衰变因子可能进入3' NCR或3' NCR核糖核蛋白结构或组成的翻译偶联变化来激活ARE介导的衰变一致。
