Seems to be involved in transcriptional silencing in heterochromatin-like complexes. Recognizes and binds histone H3 tails methylated at 'Lys-9', leading to epigenetic repression. May contribute to the association of the heterochromatin with the inner nuclear membrane through its interaction with lamin B receptor (LBR). Involved in the formation of functional kinetochore through interaction with MIS12 complex proteins. Contributes to the conversion of local chromatin to a heterochromatin-like repressive state through H3 'Lys-9' trimethylation, mediates the recruitment of the methyltransferases SUV39H1 and/or SUV39H2 by the PER complex to the E-box elements of the circadian target genes such as PER2 itself or PER1. Mediates the recruitment of NIPBL to sites of DNA damage at double-strand breaks (DSBs). Binds directly to CHAF1A. Interacts with histone H3 methylated at 'Lys-9'. Part of the E2F6.com-1 complex in G0 phase composed of E2F6, MGA, MAX, TFDP1, CBX3, BAT8, EUHMTASE1, RING1, RNF2, MBLR, L3MBTL2 and YAF2. Interacts with INCENP, TRIM28/TIF1B and SP100 (By similarity). Interacts with TIF1/TIF1A (By similarity). Interacts with MIS12 and DSN1. Can interact directly with CBX5 via the chromoshadow domain (By similarity). Interacts with KMT5B and KMT5C (By similarity). Interacts with POGZ. Interacts with CHAMP1. The large PER complex involved in the histone methylation is composed of at least PER2, CBX3, TRIM28, SUV39H1 and/or SUV39H2; CBX3 mediates the formation of the complex (By similarity). Interacts with INCENP. Interacts with NIPBL (via PxVxL motif). Interacts with LRIF1 (via PxVxL motif) (By similarity). Interacts with TTLL12 (By similarity). Interacts with ZNF263; recruited to the SIX3 promoter along with other proteins involved in chromatin modification and transcriptional corepression where it contributes to transcriptional repression (By similarity). May be associated with microtubules and mitotic poles during mitosis (Potential). Associates with euchromatin and is largely excluded from constitutive heterochromatin (By similarity). Phosphorylated by PIM1. Phosphorylated during interphase and possibly hyper-phosphorylated during mitosis.