E2F6, presumably in complex with TFDP1 (DP-1) or TFDP2 (DP-2), interacts with components of the Polycomb group (PcG) complex PRC1: BMI1, RYBP, RING1 (RING1A), PCGF2 (MEL-18) and PHC1 (mPH1) (Trimarchi et al. 2001), as well as PHC3 (Deshpande et al. 2007). The PRC1 complex may contribute to E2F6-mediated transcriptional repression. PHC3 exhibits frequent loss of heterozygosity (LoH) in primary human osteosarcoma tumors (Deshpande et al. 2007).