AIP3P AND REGULATING ACTIN ORGANIZATION

所提议的实验旨在了解肌动蛋白 细胞骨架变得极化，从而导致酵母的生长， 极化（即，直接到芽）。 细胞G1期晚期 周期，肌动蛋白细胞骨架变得定向：肌动蛋白电缆对齐， 指向最初的芽点，并在细胞处的肌动蛋白斑块中结束 皮层（皮层补丁），芽将出现。 芽的过程 位点选择和肌动蛋白细胞骨架极化需要几个 proteins. 极化肌动蛋白电缆的机制的中心， 小G蛋白Cdc42。 据认为， Cdc42通过Cdc28 CDK使其定向肌动蛋白。 这是如何实现 不知道。 在几种蛋白质中， 这个过程就是Aip 3，安贝格将其鉴定为肌动蛋白相互作用的蛋白质。 蛋白质的双杂交技术。 他认为Aip3参与了 有两个原因。首先，AIP3的缺失破坏了 肌动蛋白极化 突变体可以启动芽的形成，但不能 维持肌动蛋白极性，导致去极化生长，效率低下 分泌囊泡定位于芽位，扩大，紊乱 细胞，隔膜形成差，二倍体中随机的芽位选择， 在有丝分裂中有缺陷的核分离。 第二，Aip3本地化， 与皮质肌动蛋白重叠的位点，表明它与 极化肌动蛋白，并可能在这一过程中发挥作用。 的想法 Aip3在引导肌动蛋白在芽位点组装中起作用。 Aip3很好地定位于芽颈的观察结果支持了这一点 在肌动蛋白皮层补丁组装之前。 Aip3不是 绝对需要肌动蛋白组装在芽的网站，也不是隔蛋白 组装在芽网站，因为这两个过程发生（但与 更低的效率和保真度）。

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.