Component of the chromatin assembly factor complex (CAF-1) involved in chromatin assembly following DNA replication and DNA repair. Required for several aspects of development, including seedling growth and leaf hair differentiation. Plays a critical role in the organization of shoot apical meristem (SAM) and root apical meristem (RAM) during postembryonic development by facilitating stable maintenance of gene expression states. Seems not required to maintain transcriptional repression of heterochromatic genes. Involved in heterologous recombination. Component of the chromatin assembly factor 1 (CAF-1) complex, composed of FAS1, FAS2 and MSI1. Fasciated plants with broad, flat stems and disrupted phyllotaxy. Shoot apical meristem enlargement and altered floral development. Reduced heterochromatin content, more open conformation of euchromatin and dramatic increase of homologous recombination. Belongs to the WD repeat HIR1 family.