Regulator of biological processes that recruits a histone deacetylase to control gene transcription. May play a role in the entry into mitosis, negatively regulating the cell proliferation. Formation of stable complexes with geminiviridae replication-associated proteins may create a cellular environment which favors viral DNA replication. Interacts with RPD3I, RBAP1, the Arabidopsis cyclin CYCD3-1, the mastrevirus replication-associated protein A (RepA) and the begomovirus replication-associated protein (Rep). Ubiquitous. Expressed in 5 to 8 days after pollination endosperm and does not change significantly during later developmental stages. The C-terminal domain (743-867) is required for binding of RPD3I and RBAP1. Belongs to the retinoblastoma protein (RB) family.