INTEGRATION OF MATING WITH THE BUDDING YEAST CELL CYCLE

萌芽酵母在细胞周期的G1期交配。各自的细胞 交配型产生与细胞表面相互作用的交配信息素 相反交配型细胞上的受体。信息素与蛋白质的结合 受体触发包括改变基因在内的分化程序 转录，改变细胞形态，以及Gl细胞周期停滞。这个 开始调控点在细胞周期的G1期标志着一个尖锐的 从敏感到交配信息素到抗性的转变，直到 下一个Gl阶段。我们对此的分子基础很感兴趣 承诺事件，它整合了接合作用和细胞周期。这个 FAR1基因是交配信息素抑制所必需的。我们发现， FAR1的降解受细胞周期调节，并且降解与 磷酸化。这种控制和FAR1转录控制导致 只有在启动前的G1期才有显著的Far1蛋白积累 细胞周期。因此，FAR1的细胞周期调节可能有助于 开始时从交配信息素敏感过渡到抗性。这 暗示了细胞周期进程对所涉及的机械的负面控制 在细胞周期停滞和交配中。我们已经开始了遗传和生化 分析了控制FAR1降解的依据。这一分析 是基于我们的观察，即Far1的磷酸化先于其 降解，以及Far1的N端缺失突变体阻断 退化。我们已经确定了另一个独立阴性 整个信息素信号通路的控制。转录的 交配因子对参与交配的基因的诱导在很大程度上被阻止了 在大约开始的时间，可能是通过特定的CLN/CDC28蛋白激酶 复合体。我们希望首先从基因和基因上描述这种控制 归根结底是生物化学。

Budding yeast mate in the Gl phase of the cell cycle. Cells of each mating type produce mating pheromones that interact with cell surface receptors on cells of the opposite mating type. Binding of pheromone to receptors triggers a differentiative program including altered gene transcription, altered cell morphology, and Gl cell cycle arrest. The START regulatory point in the Gl phase of the cell cycle marks a sharp transition from sensitivity to mating pheromones to resistance until the next Gl phase. We are interested in the molecular basis of this commitment event, which integrates conjugation and the cell cycle. The FAR1 gene is essential for mating pheromone arrest. We have found that FAR1 degradation is cell-cycle regulated, and degradation correlates with phosphorylation. This control and FAR1 transcriptional control result in significant accumulation of Far1 protein only in the pre-START Gl phase of the cell cycle. Cell cycle regulation of FAR1 thus can contribute to the transition from mating pheromone sensitivity to resistance at START. This implies a negative control by cell-cycle progression on machinery involved in cell cycle arrest and mating. We have begun genetic and biochemical analysis of the basis for the control of Far1 degradation. This analysis is based on our observations that Far1 phosphorylation precedes its degradation, and that an N-terminal deletion mutant of Far1 blocks degradation. We have identified an additional independent negative control of the overall pheromone signalling pathway. Transcriptional induction by mating factor of genes involved in mating is largely blocked at about the time of START, possibly by specific Cln/Cdc28 protein kinase complexes. We wish to characterize this control, first genetically and ultimately biochemically.