Department of Biology, Villanova University, PA, USA.
FEMS Yeast Res. 2012 Dec;12(8):980-9. doi: 10.1111/1567-1364.12000. Epub 2012 Oct 2.
What steps are required for a promoter to acquire regulation by an environmental condition? We address this question by examining a promoter in Candida glabrata that is regulated by phosphate starvation and the transcription factor Pho4. The gene PMU2 encodes a secreted acid phosphatase that resulted from gene duplication events not present in other Ascomycetes, and only this gene of the three paralogs has acquired Pho4 regulation. We observe that the PMU2 promoter from C. glabrata is not functional in Saccharomyces cerevisiae, which is surprising because it is regulated by Pho4, and Pho4 is regulated in a similar manner in both species - through phosphorylation and localization. Additionally, we determine that phosphate starvation-regulated promoters in C. glabrata do not require the coactivator Pho2, which is essential to the phosphate starvation response in S. cerevisiae. We define a region of the PMU2 promoter that is important for Pho4 regulation, and this promoter region does not contain the canonical CACGTX sequence that ScPho4 utilizes for phosphate starvation-dependent transcription. However, CgPho4 utilizes CACGTX in the CgPHO84 promoter, as mutation of this sequence decreases transcription. We conclude that the acquisition of PMU2 has expanded the binding specificity of CgPho4 relative to ScPho4.
启动子需要经过哪些步骤才能被环境条件调控？我们通过研究酿酒酵母中受磷酸盐饥饿和转录因子 Pho4 调控的一个启动子来回答这个问题。PMU2 基因编码一种分泌型酸性磷酸酶，它是通过基因重复事件产生的，而其他子囊菌中并没有这些重复事件，只有这三个同源基因中的一个获得了 Pho4 的调控。我们观察到，来自光滑球拟酵母的 PMU2 启动子在酿酒酵母中没有功能，这令人惊讶，因为它受 Pho4 调控，而 Pho4 在这两个物种中的调控方式是相似的——通过磷酸化和定位。此外，我们还确定，光滑球拟酵母中受磷酸盐饥饿调控的启动子不需要共激活因子 Pho2，而 Pho2 是酿酒酵母磷酸盐饥饿反应所必需的。我们定义了 PMU2 启动子中对 Pho4 调控很重要的一个区域，这个启动子区域不包含 ScPho4 用于磷酸盐饥饿依赖转录的典型 CACGTX 序列。然而，CgPho4 在 CgPHO84 启动子中使用 CACGTX，因为这个序列的突变会降低转录。我们的结论是，PMU2 的获得扩展了 CgPho4 相对于 ScPho4 的结合特异性。
