The present invention provides mammalian retinoblastoma (Rb) protein-interacting zinc finger (RIZ) proteins, nucleic acid molecules encoding the RIZ and antibodies specific for the RIZ. The invention also provides screening assays for identifying an agent that effectively alters the association of a RIZ with a second molecule, which can bind to the RIZ. The invention also provides active fragments of RIZ containing the PR domain, which can regulate transcription. In addition, the invention provides methods for introducing a nucleic acid molecule-encoding a RIZ into a cell and for A-contacting a cell with an effective agent in order to modulate a function of a cell. Such methods are useful, for example, for inducing growth of a cardiac cell or a neuronal cell in a subject and for effecting normal growth control to a tumor cell or causing differentiation of tumor cells. The invention further provides methods for detecting a RIZ in a sample by detecting the RIZ or a nucleic acid molecule encoding the RIZ. Such methods are useful to diagnose a pathology that is characterized by an increased or decreased level of a RIZ in a cell or by expression of a mutant RIZ in a cell.
