Overproduction of PDR3 suppresses mitochondrial import defects associated with a TOM70 null mutation by increasing the expression of TOM72 in Saccharomyces cerevisiae
Overproduction of PDR3 suppresses mitochondrial import defects associated with a TOM70 null mutation by increasing the expression of TOM72 in Saccharomyces cerevisiae
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DOI：
10.1128/mcb.21.22.7576-7586.2001
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发表时间：
2001-11-01
影响因子：
5.3
通讯作者：
Bedwell, DM
中科院分区：
文献类型：
--
作者：
Koh, JY;Hájek, P;Bedwell, DM
大多数线粒体蛋白是由可切割的氨基末端靶向信号合成的，这些信号与线粒体输入机制相互作用，以促进它们从细胞质中输入。我们之前报道过f -1- atp酶β亚基前体的前体序列（pre-F(1) β）作为分子内的伴侣，在进口之前保持前体的进口能力构象（P. Hajek， J. Y. Koh， L. Jones, and D. M. Bedwell, Mol. Cell）。《圣经》17:7169-7177,1997)。我们还发现，具有最小靶向信号（delta1,2 pre-F(1)beta）的pre-F(1)beta突变形式无法有效地导入线粒体，因为它会迅速折叠成无法导入的构象。我们现在更详细地分析了将pre-F(1) β靶向信号减少到最小单位的后果。我们发现delta 1,2 pre-F(1)beta比WT pre-F(1)beta更依赖于Tom70p受体的进口，导致在15℃的不可发酵碳源上生长缺陷。使用体外线粒体蛋白导入系统的实验表明，Tom70p的功能是维持含有delta1,2 pre-F(1) β导入信号的前体处于导入能力构象。我们还发现PDR3是多效性耐药网络的转录调节因子，在tom70 Delta菌株中作为与delta1,2 pre-F(1) β相关的线粒体输入缺陷的多拷贝抑制因子。PDR3的过量产生通过增加delta1,2 pre-F(1) β进入线粒体的输入介导了这种作用。这增加了线粒体ATP合酶活性，在选择条件下恢复了突变株的生长。对线粒体外膜输入机制组分的转录模式分析表明，PDR3的过量生产增加了TOM72的表达，而TOM70的同源物研究较少。这些结果表明Tom72p具有与Tom70p重叠的功能，并且多效性耐药网络在线粒体生物发生中发挥了以前未被认识到的作用。
Most mitochondrial proteins are synthesized with cleavable amino-terminal targeting signals that interact with the mitochondrial import machinery to facilitate their import from the cytosol. We previously reported that the presequence of the F-1-ATPase beta subunit precursor (pre-F(1)beta) acts as an intramolecular chaperone that maintains the precursor in an import-competent conformation prior to import (P. Hajek, J. Y. Koh, L. Jones, and D. M. Bedwell, Mol. Cell. Biol. 17:7169-7177, 1997). We also found that a mutant form of pre-F(1)beta with a minimal targeting signal (Delta1,2 pre-F(1)beta) is inefficiently imported into mitochondria because it rapidly folds into an import-incompetent conformation. We have now analyzed the consequences of reducing the pre-F(1)beta targeting signal to a minimal unit in more detail. We found that Delta1,2 pre-F(1)beta is more dependent upon the Tom70p receptor for import than WT pre-F(1)beta is, resulting in a growth defect on a nonfermentable carbon source at 15 degreesC. Experiments using an in vitro mitochondrial protein import system suggest that Tom70p functions to maintain a precursor containing the Delta1,2 pre-F(1)beta import signal in an import-competent conformation. We also identified PDR3, a transcriptional regulator of the pleiotropic drug resistance network, as a multicopy suppressor of the mitochondrial import defects associated with Delta1,2 pre-F(1)beta in a tom70 Delta strain. The overproduction of PDR3 mediated this effect by increasing the import of Delta1,2 pre-F(1)beta into mitochondria. This increased the mitochondrial ATP synthase activity to the extent that growth of the mutant strain was restored under the selective conditions. Analysis of the transcription patterns of components of the mitochondrial outer membrane import machinery demonstrated that PDR3 overproduction increased the expression of TOM72, a little studied TOM70 homologue. These results suggest that Tom72p possesses overlapping functions with Tom70p and that the pleiotropic drug resistance network plays a previously unappreciated role in mitochondrial biogenesis.