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首页> 外文期刊>BMC Microbiology >A homeobox protein Phx1 regulates long-term survival and meiotic sporulation in Schizosaccharomyces pombe
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A homeobox protein Phx1 regulates long-term survival and meiotic sporulation in Schizosaccharomyces pombe

机译：同源盒蛋白Phx1调节粟酒裂殖酵母的长期存活和减数分裂孢子形成

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Background In the fission yeast Schizosaccharomyces pombe, the phx1+ ( p ombe h omeobo x ) gene was initially isolated as a multi-copy suppressor of lysine auxotrophy caused by depletion of copper/zinc-containing superoxide dismutase (CuZn-SOD). Overproduction of Phx1 increased the synthesis of homocitrate synthase, the first enzyme in lysine biosynthetic pathway, which is labile to oxidative stress. Phx1 has a well conserved DNA-binding domain called homeodomain at the N-terminal region and is predicted to be a transcription factor in S. pombe. However, its role has not been revealed in further detail. Here we examined its expression pattern and the phenotype of its null mutant to get clues on its function. Results Fluorescence from the Phx1-GFP expressed from a chromosomal fusion gene demonstrated that it is localized primarily in the nucleus, and is distinctly visible during the stationary phase. When we replaced the N-terminal homeobox domain of Phx1 with the DNA binding domain of Pap1, a well-characterized transcription factor, the chimeric protein caused the elevation of transcripts from Pap1-dependent genes such as ctt1+ and trr1+, suggesting that Phx1 possesses transcriptional activating activity when bound to DNA. The amount of phx1+ transcripts sharply increased as cells entered the stationary phase and was maintained at high level throughout the stationary phase. Nutrient shift down to low nitrogen or carbon sources caused phx1+ induction during the exponential phase, suggesting that cells need Phx1 for maintenance function during nutrient starvation. The Δphx1 null mutant showed decreased viability in long-term culture, whereas overproduction of Phx1 increased viability. Decrease in long-term survival was also observed for Δphx1 under N- or C-starved conditions. In addition, Δphx1 mutant was more sensitive to various oxidants and heat shock. When we examined sporulation of the Δphx1/Δphx1 diploid strain, significant decrease in the formation of meiotic spores was observed. Conclusions Phx1 is a transcriptional regulator whose synthesis is elevated during stationary phase and by nutrient starvation in S. pombe. It supports long-term survival and stress tolerance against oxidation and heat, and plays a key role in the formation of meiotic spores.
机译：背景在裂变酵母粟酒裂殖酵母中，最初分离出phx1 + （pombe h omeobo x）基因作为赖氨酸营养缺陷型的多拷贝抑制剂，其原因是铜/锌超氧化物歧化酶（ CuZn-SOD）。 Phx1的过量生产增加了纯柠檬酸合酶的合成，这是赖氨酸生物合成途径中的第一种酶，对氧化应激不稳定。 Phx1在N端区域有一个保守的DNA结合结构域，称为同源结构域，据预测是S. pombe中的转录因子。但是，它的作用尚未得到更详细的揭示。在这里，我们检查了其表达模式和无效突变体的表型，以获取有关其功能的线索。结果从染色体融合基因表达的Phx1-GFP荧光表明它主要定位在细胞核中，在固定相期间清晰可见。当我们用特征明确的转录因子Pap1的DNA结合结构域替换Phx1的N端同源异型框结构域时，嵌合蛋白导致依赖于Pap1的基因（如ctt1 + ）的转录本升高和trr1 + ，表明Phx1与DNA结合时具有转录激活活性。随着细胞进入固定期，phx1 + 转录本的数量急剧增加，并且在整个固定期均保持高水平。营养素向低氮或低碳源转移会在指数期引起phx1 + 的诱导，表明细胞在营养缺乏时需要Phx1来维持功能。 Δphx1无效突变体在长期培养中显示出活力降低，而Phx1的过量生产则提高了活力。在N饥饿或C饥饿条件下，Δphx1的长期存活率也降低了。此外，Δphx1突变体对各种氧化剂和热激更为敏感。当我们检查Δphx1/Δphx1二倍体菌株的孢子形成时，观察到减数分裂孢子形成的显着减少。结论Phx1是一种转录调节因子，在粟酒裂殖酵母的固定期和营养饥饿状态下其合成都增加。它支持长期生存以及对氧化和热的耐受性，并且在减数分裂孢子的形成中起关键作用。

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