How do cells simultaneously build different actin structures from the same building blocks?
Ingrid Billault-Chaumartin and Sophie Martin define a mechanism by which cells can simultaneously maintain distinct actin structures. This involves capping protein, a dimer that caps the end of the actin filament when these are assembled by the Arp2/3 nucleator and protects it from the action of formin proteins that assemble distinct structures. When capping protein is absent, actin structures acquire a dual identity and contain both nucleators