Abstract
Arc, a neuronal gene that is critical for synaptic plasticity, originated through the domestication of retrotransposon Gag genes and mediates intercellular messenger RNA transfer. We report high-resolution structures of retrovirus-like capsids formed by Drosophila dArc1 and dArc2 that have surface spikes and putative internal RNA-binding domains. These data demonstrate that virus-like capsid-forming properties of Arc are evolutionarily conserved and provide a structural basis for understanding their function in intercellular communication.