Whiteway M, Hougan L, Thomas D Y
Genetic Engineering Section, Biotechnology Research Institute, Montreal, Quebec, Canada.
Mol Cell Biol. 1990 Jan;10(1):217-22. doi: 10.1128/mcb.10.1.217-222.1990.
The STE4 gene of Saccharomyces cerevisiae encodes the beta subunit of the yeast pheromone receptor-coupled G protein. Overexpression of the STE4 protein led to cell cycle arrest of haploid cells. This arrest was like the arrest mediated by mating pheromones in that it led to similar morphological changes in the arrested cells. The arrest occurred in haploid cells of either mating type but not in MATa/MAT alpha diploids, and it was suppressed by defects in genes such as STE12 that are needed for pheromone response. Overexpression of the STE4 gene product also suppressed the sterility of cells defective in the mating pheromone receptors encoded by the STE2 and STE3 genes. Cell cycle arrest mediated by STE4 overexpression was prevented in cells that either were overexpressing the SCG1 gene product (the alpha subunit of the G protein) or lacked the STE18 gene product (the gamma subunit of the G protein). This finding suggests that in yeast cells, the beta subunit is the limiting component of the active beta gamma element and that a proper balance in the levels of the G-protein subunits is critical to a normal mating pheromone response.
酿酒酵母的STE4基因编码酵母信息素受体偶联G蛋白的β亚基。STE4蛋白的过表达导致单倍体细胞的细胞周期停滞。这种停滞类似于由交配信息素介导的停滞，因为它会导致停滞细胞中出现类似的形态变化。停滞发生在两种交配型的单倍体细胞中，但不在MATa/MATα二倍体细胞中，并且它被信息素应答所需的基因（如STE12）缺陷所抑制。STE4基因产物的过表达也抑制了由STE2和STE3基因编码的交配信息素受体缺陷的细胞的不育性。在过表达SCG1基因产物（G蛋白的α亚基）或缺乏STE18基因产物（G蛋白的γ亚基）的细胞中，由STE4过表达介导的细胞周期停滞被阻止。这一发现表明，在酵母细胞中，β亚基是活性βγ元件的限制成分，并且G蛋白亚基水平的适当平衡对于正常的交配信息素应答至关重要。
