Duncan R F
University of Southern California School of Pharmacy, Department of Molecular Pharmacology and Toxicology 90033, USA.
Eur J Biochem. 1995 Nov 1;233(3):784-92. doi: 10.1111/j.1432-1033.1995.784_3.x.
Treatment of cells with cordycepin (3-deoxyadenosine), an inhibitor of cytoplasmic adenylation, blocks the restoration of normal translation following heat shock. Cordycepin also reduces heat-shock protein 70 (Hsp70) protein synthesis greater than 10-fold, while having little to no effect on mRNA accumulation. Parallel analysis of the poly(A)-binding protein detects no change in its abundance during heat shock or subsequent recovery. These results suggest that normal, non-heat-shock mRNA translational repression during heat shock may be caused by deadenylation, and that readenylation is required for restoration of activity. However, three independent analyses of the adenylation status of mRNAs during heat shock and recovery indicate that no significant changes in polyadenylation occur. (a) The total poly(A) content decreases by only about 10% during heat shock; (b) the size of the poly(A) tract decreases only marginally, from an average length of 75-90 nucleotides in non-heated cells to 45-60 nucleotides during heat shock; (c) virtually all mRNAs bind to oligo d(T)-cellulose, whether extracted from normal-temperature, heat-shock or recovered cells. Our results are most consistent with a model where the process of readenylation, rather than the specific poly(A) tail length, influences translational activation during recovery, paralleling a proposed model for the activation of translation during Xenopus oocyte maturation.
用胞嘧啶核苷（3 - 脱氧腺苷）（一种细胞质腺苷酸化抑制剂）处理细胞，会阻断热休克后正常翻译的恢复。胞嘧啶核苷还会使热休克蛋白70（Hsp70）的蛋白质合成减少超过10倍，而对mRNA积累几乎没有影响。对多聚腺苷酸结合蛋白的平行分析检测到其在热休克或随后恢复过程中的丰度没有变化。这些结果表明，热休克期间正常的非热休克mRNA翻译抑制可能是由去腺苷酸化引起的，而恢复活性需要重新腺苷酸化。然而，对热休克和恢复过程中mRNA腺苷酸化状态的三项独立分析表明，多聚腺苷酸化没有显著变化。（a）热休克期间总多聚腺苷酸含量仅下降约10%；（b）多聚腺苷酸尾的长度仅略有下降，从非加热细胞中平均75 - 90个核苷酸的长度降至热休克期间的45 - 60个核苷酸；（c）几乎所有mRNA都能与寡聚d（T） - 纤维素结合，无论其是从常温、热休克还是恢复后的细胞中提取的。我们的结果与这样一种模型最为一致，即重新腺苷酸化过程而非特定的多聚腺苷酸尾长度影响恢复过程中的翻译激活，这与非洲爪蟾卵母细胞成熟过程中翻译激活的一个提出的模型相似。
