Septins and the Cell Cycle in Budding Yeast

描述(申请人提供)：在发芽酵母中发现了在细胞分裂中有缺陷的突变体。隔膜形成细丝，并在母亲和花蕾之间的颈部形成一个环。它既是母体/芽体极性的扩散屏障，又是调控蛋白的骨架。我们建议研究发芽酵母中的隔膜蛋白的结构、组装和功能。 隔素环含有细丝，用薄层电子显微镜观察，现在是旋转阴影的制剂。环在细胞周期中改变其形状和大小，并具有极性。我们将通过细胞周期研究细丝和环的结构，以及它们组装和拆卸的分子机制，使用体内和体外的方法。 纺锤体位置检查点确保有丝分裂纺锤体在退出有丝分裂之前进入母/芽颈部，随后进行细胞分裂。有丝分裂的退出是由G蛋白TEML控制的，它与只在芽中发现的全环基金Lte1相互作用。我们发现Septin突变体在将Lte1限制在芽上是有缺陷的，这与Septin的扩散屏障作用一致。我们将研究这种效应的分子机制。 纺锤体位置检查点似乎也涉及细胞质微管与颈部假定的传感器蛋白的相互作用。根据我们已发表的研究，我们假设隔膜环作为传感器的支架。为了验证这一假设，我们发现了在纺锤体位置检查点有缺陷的新突变体，并将研究这些基因如何参与纺锤体位置检查点的分子机制。 在花蕾形态发生检查点中，间隔蛋白的结构被假设为感知机制。为了验证这一假设，我们将研究与细胞周期和检查点激活相关的Septin细丝结构。

DESCRIPTION (provided by applicant): Septins were discovered as mutants defective in cell division in budding yeast. Septins form filaments and compose a ring at the neck between mother and bud. Septins function as a diffusion barrier for mother / bud polarity and as a scaffold for regulatory proteins. We propose to study septin structure, assembly, and function in budding yeast. The septin ring contains filaments, seen by thin section EM and now in rotary shadowed preparations. The ring changes its shape and size through the cell cycle, and it has polarity. We will investigate filament and ring structure through the cell cycle, and the molecular mechanisms of their assembly and disassembly, using in vivo and in vitro approaches. The spindle position checkpoint ensures that the mitotic spindle moves into the mother / bud neck before exit from mitosis occurs, followed by cell division. Mitotic exit is controlled by the G-protein, Teml, which interacts with a GEF, Lte1, found only in the bud. We discovered septin mutants defective in restriction of Lte1 to the bud, consistent with a diffusion barrier role for septins. We will investigate the molecular mechanism of this effect. The spindle position checkpoint also appears to involve the interaction of cytoplasmic microtubules with a putative sensor protein at the neck. We hypothesize that the septin ring serves as the scaffold for the sensor, based on our published studies. To test this hypothesis, we identified new mutants defective in the spindle position checkpoint, and we will study how these genes contribute to the molecular mechanism of the spindle position checkpoint. In the bud morphogenesis checkpoint, the architecture of the septins is hypothesized to be the sensing mechanism. To test this hypothesis, we will examine septin filament architecture with respect to the cell cycle and checkpoint activation.