Retinoblastoma protein-interacting zinc finger protein 1 (RIZ1), also known as PRDM2, is a SAM-dependent histone methyltransferase that specifically methylates histone H3 on lysine 9. RIZ1 contains 8 zinc-finger motifs and 1 PR domain. The RIZ gene encodes two different proteins, RIZ1 and RIZ2. RIZ1 is a tumor suppressor that can arrest the cell cycle and induce apoptosis. RIZ2 however, is a proto-oncoprotein lacking the N-terminal PR domain containing the methyltransferase activity. When RIZ1 is silenced or mutated, the reduced methyltransferase activity can lead to inheritable changes in chromatin methylation and gene expression patterns.
