A member of the argonaute siRNA chaperone (ARC) complex which is required for histone H3K9 methylation, heterochromatin assembly and siRNA generation. The ARC complex contains mostly double-stranded siRNA. Inhibits the release of the siRNA passenger strand from ago1 together with arb1. Component of the argonaute siRNA chaperone (ARC) complex composed of ago1, arb1 and arb2. Localizes to a large number of foci in both the nucleus and cytoplasm.