Effects of oxygen concentration on the expression of cytochrome c and cytochrome c oxidase genes in yeast
Effects of oxygen concentration on the expression of cytochrome c and cytochrome c oxidase genes in yeast
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DOI：
10.1074/jbc.272.23.14705
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发表时间：
1997-06-06
影响因子：
4.8
通讯作者：
Poyton, RO
中科院分区：
文献类型：
--
作者：
Burke, PV;Raitt, DC;Poyton, RO
氧是酿酒酵母中几个基因转录的重要环境调节因子，但目前尚不清楚这种酵母或其他真核生物实际上是如何感知氧的。为了解决这个问题，我们研究了氧气浓度对呼吸链末端蛋白质的几个核基因(Cyc1、CyC7、COX4、COX5a、COX5b、COX6、COX7、Cox8和COX9)表达的影响。COX5b和CyC7是低氧基因，其余是有氧基因。我们发现，这些基因的表达水平是由氧浓度本身决定的，而不仅仅是氧的存在或不存在，并且每个基因的表达都有一个低的氧阈值(0.5-1muMO-2)。对于某些需氧基因(COX4、COX5a、COX7、COX8和COX9)，在200 mM O-2(空气)和它们的氧气阈值之间，表达逐渐下降。低于这一门槛，表情就会陡然下降。对于其他(COX5a和Cyc1)，其表达水平几乎在200亩MO-2和它们的阈值之间保持不变，然后下降。低氧基因COX5b和CyC7只有在氧气浓度低于0.5muMO-2时才能表达。这些研究还表明，细胞色素c氧化酶亚基V和细胞色素c的有氧亚型基因COX5a和Cyc1，以及细胞色素c氧化酶亚基V和细胞色素c的缺氧型基因COX5b和CyC7在不同的氧浓度下共表达，并在极低的氧浓度下开启或关闭。通过将细胞从一种氧气浓度转移到另一种氧气浓度，我们发现，有氧基因的诱导比缺氧基因的诱导更快，两种类型的基因的转录本都被迅速翻转。这些发现对酵母细胞色素C氧化酶的功能、生物发生和氧感应的FAR模型具有重要的意义。
Oxygen is an important environmental regulator for the transcription of several genes in Saccharomyces cerevisiae, but it is not yet clear how this yeast or other eukaryotes actually sense oxygen. To begin to address this we have examined the effects of oxygen concentration on the expression of several nuclear genes (CYC1, CYC7, COX4, COX5a, COX5b, COX6, COX7, COX8, and COX9) for proteins of the terminal portion of the respiratory chain. COX5b and CYC7 are hypoxic genes; the rest are aerobic genes. We have found that the level of expression of these genes is determined by oxygen concentration per se and not merely the presence or absence of oxygen and that each of these genes has a low oxygen threshold (0.5-1 mu M O-2) for expression. For some aerobic genes (COX4, COX5a, COX7, COX8, and COX9) there is a gradual decline in expression between 200 mu M O-2 (air) and their oxygen threshold. Below this threshold expression drops precipitously. For others (COX5a and CYC1) the level of expression is nearly constant between 200 mu M O-2 and their threshold and then drops off. The hypoxic genes COX5b and CYC7 are not expressed until the oxygen concentration is below 0.5 mu M O-2. These studies have also revealed that COX5a and CYC1, the genes for the aerobic isoforms of cytochrome c oxidase subunit V and cytochrome c, and COX5b and CYC7, the genes for the hypoxic isoforms of cytochrome c oxidase subunit V and cytochrome c, are coexpressed at a variety of oxygen concentrations and switch on or off at extremely low oxygen concentrations. By shifting cells from one oxygen concentration to another we have found that aerobic genes are induced faster than hypoxic genes and that transcripts from both types of gene are turned over quickly. These findings have important implications for cytochrome c oxidase function and biogenesis and far models of oxygen sensing in yeast.