Clark K L, Sprague G F
Institute of Molecular Biology, University of Oregon, Eugene 97403.
Mol Cell Biol. 1989 Jun;9(6):2682-94. doi: 10.1128/mcb.9.6.2682-2694.1989.
Saccharomyces cerevisiae haploid cells, alpha and a, mate after being appropriately stimulated by the pheromone secreted by the opposite cell type (a-factor and alpha-factor, respectively). The binding of a pheromone to its receptor is a signal that initiates a series of intracellular changes that lead to the specific physiological alterations required for mating. To identify components of the signal transduction pathway, we sought pseudorevertants that restored mating competence to receptor mutants (MAT alpha ste3::LEU2). The suppressor srm1-1 was isolated as a recessive mutation that conferred temperature-sensitive growth to all strains and mating ability to MAT alpha ste3::LEU2 strains at the nonpermissive temperature. In addition, when srm1-1 mutants were shifted to the nonpermissive temperature, they exhibited two phenotypes characteristic of pheromone response, induction of FUS1 transcription and accumulation of cells in the G1 phase of the cell cycle. The srm1-1 mutation also suppressed a deletion of the alpha-factor-receptor gene in a cells. Together, these phenotypes suggest that the wild-type SRM1 product is a component of the pheromone response pathway. Deletion of STE4 or STE5, which are required in both haploid cell types for mating and response to pheromone, was not suppressed by srm1-1, suggesting that the SRM1 product may function before the STE4 and STE5 products. SRM1 is an essential gene and is expressed in both haploid cell types as well as in the product of their mating, a/alpha diploids. Homozygous srm1-1 a/alpha diploids were temperature sensitive although they did not arrest in G1. Thus, the SRM1 product may also have a role in the vegetative life cycle of cells.
酿酒酵母单倍体细胞，α型和a型，在受到相反细胞类型分泌的信息素（分别为a-因子和α-因子）的适当刺激后进行交配。信息素与其受体的结合是一个信号，它引发一系列细胞内变化，导致交配所需的特定生理改变。为了鉴定信号转导途径的组成成分，我们寻找能使受体突变体（MATα ste3::LEU2）恢复交配能力的假回复突变体。抑制子srm1-1作为一个隐性突变被分离出来，它使所有菌株在非允许温度下生长对温度敏感，并使MATα ste3::LEU2菌株在非允许温度下具有交配能力。此外，当srm1-1突变体转移到非允许温度时，它们表现出信息素反应的两种特征性表型，即FUS1转录的诱导和细胞在细胞周期G1期的积累。srm1-1突变也抑制了a细胞中α-因子受体基因的缺失。总之，这些表型表明野生型SRM1产物是信息素反应途径的一个组成成分。STE4或STE5的缺失在两种单倍体细胞类型中对于交配和对信息素的反应都是必需的，srm1-1不能抑制这种缺失，这表明SRM1产物可能在STE4和STE5产物之前起作用。SRM1是一个必需基因，在两种单倍体细胞类型以及它们交配的产物a/α二倍体中都有表达。纯合的srm1-1 a/α二倍体对温度敏感，尽管它们不会在G1期停滞。因此，SRM1产物可能在细胞的营养生命周期中也起作用。
