Department of Pathology, School of Medicine, University of Utah, Salt Lake City, Utah 84132, USA.
J Biol Chem. 2010 Apr 2;285(14):10232-42. doi: 10.1074/jbc.M109.096859. Epub 2010 Feb 5.
Deletion of two homologous genes, MRS3 and MRS4, that encode mitochondrial iron transporters affects the activity of the vacuolar iron importer Ccc1. Ccc1 levels are decreased in Deltamrs3Deltamrs4 cells, but the activity of the transporter is increased, resulting is reduced cytosolic iron. Overexpression of CCC1 in Deltamrs3Deltamrs4 cells results in a severe growth defect due to decreased cytosolic iron, referred to as the mitochondria-vacuole signaling (MVS) phenotype. Mutants were identified that suppress the MVS growth defect, and FRA1 was identified as a gene that suppresses the MVS phenotype. Overexpression of FRA1 suppresses altered transition metal metabolism in Deltamrs3Deltamrs4 cells, whereas deletion of FRA1 is synthetically lethal with Deltamrs3Deltamrs4. Fra1 binds to Tsa1, which encodes a thioredoxin-dependent peroxidase. Deletion of TSA1 or TRR1 is synthetically lethal in Deltamrs3Deltamrs4 cells, suggesting that Deltamrs3Deltamrs4 cells generate reactive oxygen metabolites. The generation of reactive oxygen metabolites in Deltamrs3Deltamrs4 cells was confirmed by use of the reporter molecule 2',7'-dichlorodihydrofluorescein diacetate. These results suggest that mitochondria-induced oxidant damage is responsible for activating Ccc1 and that Fra1 and Tsa1 can reduce oxidant damage.
两个同源基因 MRS3 和 MRS4 的缺失，它们编码线粒体铁转运体，会影响液泡铁转运体 Ccc1 的活性。在Δmrs3Δmrs4 细胞中 Ccc1 水平降低，但转运体的活性增加，导致细胞质铁减少。在Δmrs3Δmrs4 细胞中过表达 CCC1 会导致由于细胞质铁减少而出现严重的生长缺陷，这被称为线粒体-液泡信号（MVS）表型。鉴定出了能够抑制 MVS 生长缺陷的突变体，并且发现 FRA1 是一个能够抑制 MVS 表型的基因。FRA1 的过表达能够抑制Δmrs3Δmrs4 细胞中过渡金属代谢的改变，而 fra1 的缺失与Δmrs3Δmrs4 是合成致死的。Fra1 与编码硫氧还蛋白依赖过氧化物酶的 Tsa1 结合。TSA1 或 TRR1 的缺失在Δmrs3Δmrs4 细胞中是合成致死的，这表明Δmrs3Δmrs4 细胞会产生活性氧代谢物。通过使用报告分子 2'，7'-二氯二氢荧光素二乙酸酯证实了Δmrs3Δmrs4 细胞中活性氧代谢物的产生。这些结果表明，线粒体诱导的氧化损伤负责激活 Ccc1，而 Fra1 和 Tsa1 可以减少氧化损伤。
