PUFD is the minimal domain at the C-terminus of BCORL (BCL6 corepressor) that is needed for binding and giving specificity to some of the PCGF proteins, polycomb-group RING finger homologs. PUFD binds to the RAWUL (RING finger- and WD40-associated ubiquitin-like) domain of the particular PCGF PCGF1, pfam16207. Polycomb group proteins form repressive complexes (PRC) that mediate epigenetic modifications of histones. In humans there are many different PCGF homologs whose functions all vary, but the direct binding partner of PCGF1 is BCOR. BCOR has emerged as an important player in development and health.