Composite actin nucleator composed of formin Bni1, Bud6, and Aip5. In the WT, Aip5 collaborates with Bud6 and Bni1 to form a composite actin nucleator. Bni1 recruits profilin–actin complexes, whereas Aip5 stabilizes the nascent filament and caps its pointed end, thereby enhancing nucleation efficiency and promoting actin cable growth. In the aip5Δbud6Δ, disruption of the Aip5–Bud6 interaction compromises actin nucleation, bundling, and thereby cable organization.