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 apical meristem maintenance by regulating the durations of the S- and G2-phases of the cell cycle through its chromatin assembly activity. Component of the chromatin assembly factor 1 (CAF-1) complex, composed of FSM (FAS1), FAS2 and MSI1. In embryo, expressed in leaf primordia, coleoptile and radicle. In seedlings, expressed in cell division zone of roots, SAM and leaf primordia. Expressed in floral organ primordia. Cell cycle-regulated, showing a peak in the G1-phase. Dwarf and weak seedling that dies during vegetative phase. Belongs to the CHAF1A family. Was originally thought to correspond to two different genes. Was originally thought to correspond to two different genes.