Takemura Reiko, Inoue Yoshiharu, Izawa Shingo
Laboratory of Molecular Microbiology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
J Cell Sci. 2004 Aug 15;117(Pt 18):4189-97. doi: 10.1242/jcs.01296. Epub 2004 Jul 27.
Ethanol stress (10% v/v) causes selective mRNA export in Saccharomyces cerevisiae in a similar manner to heat shock (42 degrees C). Bulk poly(A)(+) mRNA accumulates in the nucleus, whereas heat shock protein mRNA is exported under such conditions. Here we investigated the effects of stress on mRNA export factors. In cells treated with ethanol stress, the DEAD box protein Rat8p showed a rapid and reversible change in its localization, accumulating in the nucleus. This change correlated closely with the blocking of bulk poly(A)(+) mRNA export caused by ethanol stress. We also found that the nuclear accumulation of Rat8p is caused by a defect in the Xpo1p/Crm1p exportin. Intriguingly, the localization of Rat8p did not change in heat shocked cells, suggesting that the mechanisms blocking bulk poly(A)(+) mRNA export differ for heat shock and ethanol stress. These results suggest that changes in the localization of Rat8p contribute to the selective export of mRNA in ethanol stressed cells, and also indicate differences in mRNA export between the heat shock response and ethanol stress response.
乙醇胁迫（10% v/v）在酿酒酵母中引起选择性mRNA输出，其方式与热激（42℃）相似。大量的聚腺苷酸（poly(A)）mRNA积聚在细胞核中，而热激蛋白mRNA在这种条件下会输出到细胞核外。在此，我们研究了胁迫对mRNA输出因子的影响。在用乙醇胁迫处理的细胞中，DEAD盒蛋白Rat8p的定位出现快速且可逆的变化，积聚在细胞核中。这种变化与乙醇胁迫导致的大量聚腺苷酸（poly(A)）mRNA输出受阻密切相关。我们还发现，Rat8p的核内积聚是由输出蛋白Xpo1p/Crm1p的缺陷引起的。有趣的是，Rat8p在热激细胞中的定位没有变化，这表明热激和乙醇胁迫导致大量聚腺苷酸（poly(A)）mRNA输出受阻的机制不同。这些结果表明，Rat8p定位的变化有助于乙醇胁迫细胞中mRNA的选择性输出，也表明热激反应和乙醇胁迫反应在mRNA输出方面存在差异。
