DiDomenico B J, Bugaisky G E, Lindquist S
Proc Natl Acad Sci U S A. 1982 Oct;79(20):6181-5. doi: 10.1073/pnas.79.20.6181.
When Drosophila cells are shifted from 25 degrees C to 37 degrees C, protein synthesis is rapidly redirected from the complex pattern characteristic of normal growth to the simple pattern of heat shock proteins (HSPs). On return to 25 degrees C, synthesis of normal proteins is gradually reactivated and that of HSPs is repressed. In quantifying many different recovery experiments, we found that preexisting mRNAs always behaved as a cohort, with messages for different proteins returning to translation at the same rate. Heat shock mRNAs (HS mRNAs), on the other hand, never behaved as a cohort. Their repression was asynchronous, with translation of hsp70 always the first and translation of hsp82 always the last to be repressed. Although recovery times varied enormously (depending on the severity of the heat treatment), repression of hsp70 was always correlated with restoration of normal synthesis, suggesting a link between the two events, hsp70 repression was not simply due to competition with reactivated 25 degrees C mRNAs. A general decline in the translation efficiency of hsp70 mRNA was not observed. Instead, an increasing number of messages were translationally inactivated, while those remaining in the translational pool retained full ribosome loading. Unlike inactive 25 degrees C mRNAs, which are stable during heat shock, inactive HSP mRNAs are degraded during recovery.
当果蝇细胞从25摄氏度转移至37摄氏度时，蛋白质合成迅速从正常生长特有的复杂模式转向热休克蛋白（HSP）的简单模式。回到25摄氏度后，正常蛋白质的合成逐渐重新激活，而热休克蛋白的合成则受到抑制。在对许多不同的恢复实验进行量化时，我们发现预先存在的mRNA总是作为一个群体表现，不同蛋白质的信使以相同的速率恢复翻译。另一方面，热休克mRNA（HS mRNA）从不作为一个群体表现。它们的抑制是异步的，hsp70的翻译总是最先被抑制，而hsp82的翻译总是最后被抑制。尽管恢复时间差异极大（取决于热处理的严重程度），但hsp70的抑制总是与正常合成的恢复相关，这表明这两个事件之间存在联系，hsp70的抑制并非仅仅是由于与重新激活的25摄氏度mRNA竞争。未观察到hsp70 mRNA的翻译效率普遍下降。相反，越来越多的信使在翻译上失活，而那些留在翻译池中的信使则保持完全的核糖体负载。与在热休克期间稳定的失活25摄氏度mRNA不同，失活的热休克蛋白mRNA在恢复过程中会被降解。
