AIP3P AND REGULATING ACTIN ORGANIZATION

拟议的实验旨在了解肌动蛋白是如何 细胞骨架极化，从而导致酵母的生长 极化的(即，直达萌芽)。在细胞的G1期后期 循环，肌动蛋白细胞骨架变得定向：肌动蛋白电缆排列并 指向刚萌芽的部位，并在细胞处以肌动蛋白的斑块结束 皮质(皮质斑块)，芽将在那里出现。萌芽过程 部位选择和肌动蛋白细胞骨架极化需要几个 蛋白质。是极化肌动蛋白电缆和 Patches是一种小G蛋白，即CDC42。被认为是激活了 CDC42通过CDC28CDK使其定向肌动蛋白。如何实现这一目标 是未知的。在几种已经涉及到的蛋白质中， 这个过程是Aip3，Amberg认为它是一个肌动蛋白相互作用的过程 蛋白质与2-杂交技术。他认为Aip3牵涉其中 肌动蛋白极化有两个原因。首先，删除AIP3会中断 肌动蛋白极化。突变体可以启动芽的形成，但不能 维持肌动蛋白的极性，导致去极化生长，效率低下 将分泌小泡定位于芽位，增大，杂乱 细胞，隔膜形成差，在二倍体中随机选择芽位， 有丝分裂中有缺陷的核分离。第二，Aip3本地化到 与皮质肌动蛋白重叠的部位，表明它与 极化肌动蛋白，并可能在这一过程中发挥作用。有这样的想法 Aip3在花蕾部位的肌动蛋白组装中起着指导作用 由观察到的Aip3很好地定位在蕾颈上支持 在肌动蛋白皮质贴片聚集在那里之前。然而，Aip3并非如此 在芽位组装肌动蛋白是绝对必需的，也不是隔膜蛋白所必需的 在萌芽部位组装，因为这两个过程都发生(但在 效率和保真度较低)。

The proposed experiments are aimed at understanding how the actin cytoskeleton becomes polarized, thereby causing growth of yeast to be polarized (i.e., direct to the bud). Late in the G1 phase of the cell cycle, the actin cytoskeleton becomes oriented: actin cables align and point to the incipient bud site, and end in patches of actin at the cell cortex (cortical patches) where the bud will emerge. The process of bud site selection and actin cytoskeleton polarization requires several proteins. Central to the mechanism that polarizes actin cables and patches is the small G-protein Cdc42. It is thought that activation of Cdc42 by the Cdc28 CDK causes it to orient actin. How this is achieved is not known. Among the several proteins that have been implicated in this process is Aip3, which Amberg identified as an actin-interacting protein with the 2-hybrid technique. He believes that Aip3 is involved in actin polarization for two reasons. First, deletion of AIP3 disrupts actin polarization. Mutants can initiate bud formation, but cannot maintain actin polarity, resulting in depolarized growth, inefficient targeting of secretory vesicles to the bud site, enlarged, disorganized cells, poor septum formation, random bud-site selection in diploids, defective nuclear segregation in mitosis. Second, Aip3 localizes to sites that overlap cortical actin, suggesting that it is associated with polarized actin and could play a role in the process. The idea that Aip3 plays a role in directing actin assembly at the bud site is supported by the observation that Aip3 localizes to the bud neck well before actin cortical patches assemble there. However, Aip3 is not absolutely required for actin assembly at the bud site, nor for septin assembly at the bud site, since both of these processes occur (but with less efficiency and fidelity) in Aip3 mutants.