Cellular actin arrays are often highly organized, with characteristic patterns critical to their in vivo functions, yet the mechanisms for establishing these higher order geometries remain poorly understood. In Saccharomyces cerevisiae, formin-polymerized actin cables are spatially organized and aligned along the mother–bud axis to facilitate polarized vesicle traffic. Here, we show that the bud neck–associated F-BAR protein Hof1, independent of its functions in regulating the formin Bnr1, binds to actin filaments and organizes actin cables in vivo. Hof1 bundles actin filaments and links them to septins in vitro. F-actin binding is mediated by the “linker” domain of Hof1, and its deletion leads to cable organization defects in vivo. Using superresolution imaging, we show that Hof1 and septins are patterned at the bud neck into evenly spaced axial pillars (∼200 nm apart), from which actin cables emerge and grow into the mother cell. These results suggest that Hof1, while bound to septins at the bud neck, not only regulates Bnr1 activity, but also binds to actin cables and aligns them along the mother–bud axis. More broadly, these findings provide a strong example of how an actin regulatory protein can be spatially patterned at the cell cortex to govern actin network geometry.

细胞肌动蛋白阵列通常是高度有组织的，具有对其体内功能至关重要的特征模式，但建立这些高阶几何结构的机制仍然知之甚少。在酿酒酵母中，formin 聚合的肌动蛋白电缆在空间上组织并沿母芽轴排列，以促进极化囊泡交通。在这里，我们展示了芽颈相关的 F-BAR 蛋白 Hof1，独立于其调节 Formin Bnr1 的功能，与肌动蛋白丝结合并在体内组织肌动蛋白电缆。Hof1 捆绑肌动蛋白丝并将它们在体外与 septins 联系起来。F-肌动蛋白结合由 Hof1 的“接头”域介导，其缺失导致体内电缆组织缺陷。使用超分辨率成像，我们显示 Hof1 和 septins 在芽颈形成均匀间隔的轴柱（相距约 200 nm），肌动蛋白电缆从中出现并生长到母细胞中。这些结果表明 Hof1 虽然在芽颈与 septins 结合，但不仅调节 Bnr1 的活性，但也与肌动蛋白电缆结合并沿母芽轴排列。更广泛地说，这些发现提供了一个强有力的例子，说明肌动蛋白调节蛋白如何在细胞皮层进行空间模式化以控制肌动蛋白网络几何形状。