Michaelis S, Herskowitz I
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448.
Mol Cell Biol. 1988 Mar;8(3):1309-18. doi: 10.1128/mcb.8.3.1309-1318.1988.
The Saccharomyces cerevisiae pheromone a-factor is produced by a cells and interacts with alpha cells to cause cell cycle arrest and other physiological responses associated with mating. Two a-factor structural genes, MFA1 and MFA2, have been previously cloned with synthetic probes based on the a-factor amino acid sequence (A. Brake, C. Brenner, R. Najarian, P. Laybourn, and J. Merryweather, cited in M.-J. Gething [ed.], Protein transport and secretion, 1985). We have examined the function of these genes in a-factor production and mating by construction and analysis of chromosomal null mutations. mfa1 and mfa2 single mutants each exhibited approximately half the wild-type level of a-factor activity and were proficient in mating, whereas the mfa1 mfa2 double mutant produced no a-factor and was unable to mate. These results demonstrate that both genes are functional, that each gene makes an equivalent contribution to the a-factor activity and mating capacity of a cells, and that a-factor plays an essential role in mating. Strikingly, exogenous a-factor did not alleviate the mating defect of the double mutant, suggesting that an a cell must be producing a-factor to be an effective mating partner.
酿酒酵母信息素α-因子由a细胞产生，并与α细胞相互作用，导致细胞周期停滞以及与交配相关的其他生理反应。此前，基于α-因子氨基酸序列，利用合成探针克隆出了两个α-因子结构基因MFA1和MFA2（A. 布雷克、C. 布伦纳、R. 纳贾里安、P. 莱伯恩和J. 梅里韦瑟，引自M.-J. 格辛[编]，《蛋白质转运与分泌》，1985年）。我们通过构建和分析染色体缺失突变体，研究了这些基因在α-因子产生和交配过程中的功能。mfa1和mfa2单突变体各自表现出约为野生型水平一半的α-因子活性，且交配能力正常，而mfa1 mfa2双突变体不产生α-因子，无法进行交配。这些结果表明，两个基因均具有功能，每个基因对a细胞的α-因子活性和交配能力贡献相当，且α-因子在交配过程中起关键作用。引人注目的是，外源性α-因子并不能缓解双突变体的交配缺陷，这表明a细胞必须自身产生α-因子才能成为有效的交配伙伴。
