Multifaceted “composite” actin nucleator orchestrates polymerization via dynamic assembly

In this issue, Magliozzi et al. (https://doi.org/10.1083/jcb.202505039) describe a novel actin nucleation mechanism involving an Aip5-Bud6-Bni1 "composite nucleator," which binds both the formin-mediated barbed end and Aip5-associated pointed end, enabling coordinated filament elongation and maintaining actin cable thickness.