The PRDM family members are characterized by the presence of a PR (positive regulatory) domain and multiple zinc finger (ZnFg) domains. The PR domain defines a family of transcription factors involved in cell differentiation and tumorigenesis. PRDM proteins are either epigenetic modifiers in their own right or else they recruit third party chromatin modifiers - e.g. histone deacetylases (HDACs), histone lysine MTases or histone arginine MTases - to regulate cell type-specific gene expression in various tissues (PRDM4 as an HDAC-associated transcriptional repressor that modulates cell cycle progression.