Zitomer R S, Carrico P, Deckert J
Department of Biological Sciences, University at Albany/SUNY, USA.
Kidney Int. 1997 Feb;51(2):507-13. doi: 10.1038/ki.1997.71.
Baker's yeast, Saccharomyces cerevisiae, can adapt to growth under severe oxygen limitation. Two regulatory systems are described here that control this adaptation. The first involves a heme-dependent repression mechanism. Cells sense hypoxia through the inability to maintain oxygen-dependent heme biosynthesis. Under aerobic conditions, heme accumulates and serves as an effector for the transcriptional activator Hap1. The heme-Hap1 complex activates transcription of the ROX1 gene that encodes a repressor of one set of hypoxic genes. Under hypoxic conditions, heme levels fall, and a heme-deficient Hap1 complex represses ROX1 expression. As a consequence, the hypoxic genes are derepressed. The second regulatory system activates gene expression in response to a variety of stress conditions, including oxygen limitation. Oxygen sensing in this system is heme-independent. The same DNA sequence mediates transcriptional activation of each stress signal.
面包酵母，即酿酒酵母，能够适应在严重氧气限制条件下生长。本文描述了两种控制这种适应性的调节系统。第一种涉及血红素依赖性抑制机制。细胞通过无法维持依赖氧气的血红素生物合成来感知缺氧。在有氧条件下，血红素积累并作为转录激活因子Hap1的效应物。血红素-Hap1复合物激活ROX1基因的转录，该基因编码一组缺氧基因的阻遏物。在缺氧条件下，血红素水平下降，血红素缺乏的Hap1复合物抑制ROX1表达。因此，缺氧基因被解除抑制。第二种调节系统响应包括氧气限制在内的多种应激条件激活基因表达。该系统中的氧气感知不依赖血红素。相同的DNA序列介导每个应激信号的转录激活。
